earlgrey: Add static stack size verification tooling and firmware tests

[anthonychen1251]

This PR introduces an automated, compile-time static stack size analysis tooling for pw_kernel userspace processes on OpenTitan earlgrey firmware (hwe and transport).

In pw_kernel, each process has a fixed static RAM allocation (ram_size_bytes) declared in system.json5 and enforced by hardware PMP regions.

Previously, determining the required RAM for a new or modified process required guesswork. This tooling reconstructs the caller-to-callee call graph, computes the worst-case cumulative stack depth for each process protection domain, and enforces safety margins at compile time.

• Known Limitations
  Dynamic Indirect Jumps (jalr): The static call-graph reconstructor parses disassembly to identify direct or PC-relative calls (such as jal or auipc + jalr ). However, dynamic indirect calls—including dynamic trait objects (&dyn Trait) using vtables or standard function pointers (fn())—retrieve target addresses at runtime via CPU registers (jalr rs1). Since these lack static symbol labels, they remain unresolvable through pure disassembly and are excluded from the cumulative depth calculation.

When running bazel test //target/earlgrey/firmware/transport:stack_size_transport, the tool produces a detailed report:

================================================================================
  STATIC STACK SIZE & CALL GRAPH VERIFICATION REPORT: App 'transport'
================================================================================
Binary: target/earlgrey/firmware/transport/transport
Config: target/earlgrey/firmware/transport/system.json5
Headroom buffer: 0 bytes

WARNING: Unresolved indirect jump(s) detected in reachable call paths:
  ┌─ Process: flash_server                                 
  ├── Function: _ZN44_$LT$u32$u20$as$u20$zfmt..format..Format$GT$3fmt17h473a47ead3eb0cb0E (2 indirect jump(s): a0, a2)
  ┌─ Process: logmgr
  ├── Function: _ZN4core3fmt5write17hfa250156eaa22698E (5 indirect jump(s): a3, a4, a3)
  ┌─ Process: platform
  ├── Function: _ZN4core3fmt5write17hfa250156eaa22698E (5 indirect jump(s): a3, a4, a3)
  ┌─ Process: sysmgr      
  ├── Function: _ZN4core3fmt5write17hfa250156eaa22698E (5 indirect jump(s): a3, a4, a3)
  ├── Function: _ZN4zfmt6format8fmt_uint17hdc28bddb54f49ae5E (2 indirect jump(s): a0, a2)                                                                                                                                                      
  ┌─ Process: updatemgr                                    
  ├── Function: _ZN44_$LT$u32$u20$as$u20$zfmt..format..Format$GT$3fmt17hb528abe7c7e1dd22E (2 indirect jump(s): a0, a2)
  ┌─ Process: usbmgr                                                                                                                                                                                                                           
  ├── Function: _ZN4zfmt6format8fmt_uint17hdb038c641794a7dbE (2 indirect jump(s): a0, a2)
  ├── Function: _ZN69_$LT$usbmgr..MyDescriptors$u20$as$u20$usb_stack..DescriptorSource$GT$10get_string17h622354532458fa85E (1 indirect jump(s): a3)
  ├── Function: _ZN6usbmgr13_inner_usbmgr17he8d7aaba7a3a4c07E (3 indirect jump(s): a0, a0, a0)                                                                                                                                                 
  Note: Dynamic dispatch (e.g. &dyn Trait, fn() pointers) cannot be statically traced.                         
        Callee frames beyond these calls are not included in cumulative stack depth. 

Process Allocation Budgets:
  - flash_server   : RAM =   4096 B | Max Allowed Stack =   4096 B
  - logmgr         : RAM =   4096 B | Max Allowed Stack =   4096 B
  - platform       : RAM =   4096 B | Max Allowed Stack =   4096 B
  - sysmgr         : RAM =   4096 B | Max Allowed Stack =   4096 B
  - updatemgr      : RAM =   4096 B | Max Allowed Stack =   4096 B
  - usbmgr         : RAM =  16384 B | Max Allowed Stack =  16384 B
  - [shared/common]: Min Process Budget =   4096 B

  ┌─ Process: logmgr (Peak Stack:  3504 B | Margin:   592 B / 4096 B)                                 
  ├── _entry_logmgr (16 B)            
  ├── _ZN6logmgr13_inner_logmgr17hb0e2687dbe804973E (2992 B)                                                        
  ├── _ZN6logmgr15service_uart_tx17haec1968fbeeef0a0E (448 B)                                                          
  └── _ZN9util_zfmt6buffer18LogBuffer$LT$_$GT$15next_frame_size17hb5cfe96c90154884E (48 B)                                                                                                                                                     
                                                                                                                       
  ┌─ Process: platform (Peak Stack:   656 B | Margin:  3440 B / 4096 B)                                                
  ├── _entry_platform (16 B)       
  ├── _ZN8platform15_inner_platform17hafea2982faf8e10fE (256 B)                                                        
  ├── _ZN4zfmt6output11binary_send17h70931ea870ecb1a5E (368 B)                                                                                                                                                                                 
  ├── memcpy (0 B)                                         
  └── _ZN17compiler_builtins3mem6memcpy17h6e18710bad54b5dfE (16 B)                                                     
                                                                                                                                                                                                                                               
  ┌─ Process: sysmgr (Peak Stack:  2544 B | Margin:  1552 B / 4096 B)
  ├── _entry_sysmgr (16 B)                           
  ├── _ZN6sysmgr13_inner_sysmgr17ha57e7cacbc68199fE (1456 B)                                                           
  ├── _ZN22earlgrey_sysmgr_server12SysmgrServer10handle_one17hfbbc53502d3e6ae7E (448 B)                                
  ├── _ZN4sha26sha25611compress25617h8ec77f7fe100458aE (576 B)                                                         
  └── _ZN4sha26sha2564soft8schedule17h12deaa7b8c96a277E (48 B)      
                                                           
  ┌─ Process: updatemgr (Peak Stack:  2928 B | Margin:  1168 B / 4096 B)                                               
  ├── _entry_updatemgr (16 B)                                                                                          
  ├── _ZN9updatemgr16_inner_updatemgr17hb4d9637b35ce00b3E (2352 B)     
  ├── _ZN4zfmt6output9text_send17hb01a01403afd64f7E (176 B)                                                            
  ├── _ZN4zfmt6output11binary_send17hbc0ebf3dc00068bfE (368 B)                                                         
  ├── memcpy (0 B)                                                                                                     
  └── _ZN17compiler_builtins3mem6memcpy17h6e18710bad54b5dfE (16 B)        
                                                                                                                       
  ┌─ Process: usbmgr (Peak Stack:  7056 B | Margin:  9328 B / 16384 B)
  ├── _entry_usbmgr (16 B)                                                                                             
  ├── _ZN6usbmgr13_inner_usbmgr17he8d7aaba7a3a4c07E (4912 B)
  ├── _ZN91_$LT$usbmgr..dfu..EarlgreyDfuHandler$LT$IPC$GT$$u20$as$u20$protocol_usb_dfu..DfuHandler$GT$6upload17h3db78fd8d29c7cf0E (1552 B)                                  
  ├── _ZN4zfmt6output9text_send17hd9ef02f9e4180e04E (176 B)                                                            
  ├── _ZN4zfmt6output11binary_send17h6f64ba04ee6f8cbfE (352 B)                                                                                                                                                                                 
  └── _ZN72_$LT$util_zfmt..IpcLogger$LT$IPC$GT$$u20$as$u20$zfmt..logger..Logger$GT$13send_vectored17h98cbb7746313bff0E (48 B)                                                                                                                  
                                                                                                                       
Peak Individual Function Frame by Process:                                                                             
  - flash_server   : Peak =  2224 B (Margin:  1872 B) | Function: _ZN12flash_server19_inner_flash_server17hef961fd204c07fc6E                                                                                                                   
  - logmgr         : Peak =  2992 B (Margin:  1104 B) | Function: _ZN6logmgr13_inner_logmgr17hb0e2687dbe804973E        
  - platform       : Peak =   256 B (Margin:  3840 B) | Function: _ZN8platform15_inner_platform17hafea2982faf8e10fE    
  - sysmgr         : Peak =  1456 B (Margin:  2640 B) | Function: _ZN6sysmgr13_inner_sysmgr17ha57e7cacbc68199fE        
  - updatemgr      : Peak =  2352 B (Margin:  1744 B) | Function: _ZN9updatemgr16_inner_updatemgr17hb4d9637b35ce00b3E  
  - usbmgr         : Peak =  4912 B (Margin: 11472 B) | Function: _ZN6usbmgr13_inner_usbmgr17he8d7aaba7a3a4c07E
  - [shared/common]: Peak =  1552 B (Margin:  2544 B) | Function: _ZN91_$LT$usbmgr..dfu..EarlgreyDfuHandler$LT$IPC$GT$$u20$as$u20$protocol_usb_dfu..DfuHandler$GT$6upload17h3db78fd8d29c7cf0E  

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PASSED: All cumulative call stacks and function frames conform to allocated process budgets.
================================================================================