Fix: Condition is not strictly checked on options-general.php file

[snehapatil2001]

Trac ticket: https://core.trac.wordpress.org/ticket/57030

Description

• Fixes a strict comparison issue in options-general.php where the $current_offset variable was not being strictly compared as an integer.
• This issue could lead to unexpected behavior when comparing the gmt_offset option, especially when it could be interpreted as different types such as string or float.

Changes Made

• Adjusted the comparison of $current_offset to ensure it is strictly compared as an integer 0.
• Updated logic to handle cases where gmt_offset may vary in type (integer, string, or float).
• Introduced unit tests to validate the behavior across different gmt_offset scenarios.

Added Unit Tests

• Created gmtOffset.php file to house unit tests specifically targeting the gmt_offset behavior.
• Covered scenarios such as integer 0, string '0', negative float values, and invalid string inputs for gmt_offset.

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