TimeZone initialization and validation improvements

[shial4]

This pull request improves the robustness and correctness of the TimeZone implementation in SkipFoundation, particularly around initialization and abbreviation handling. The changes ensure that invalid identifiers and abbreviations are handled gracefully, improve compatibility with Java's timezone APIs, and expand test coverage.

TimeZone initialization and validation improvements:

• Updated TimeZone.init(identifier:) and TimeZone.init(abbreviation:) to detect and reject unknown or invalid identifiers and abbreviations, addressing a quirk where Java returns a default "GMT" timezone for unknown values.
• Improved TimeZone.init(secondsFromGMT:) to validate the seconds offset (must be within ±18 hours) and construct the correct GMT identifier string, ensuring compatibility with Swift Foundation constraints.

Abbreviation support and mapping:

• Populated TimeZone.abbreviationDictionary with a comprehensive mapping of common timezone abbreviations to their canonical identifiers, enabling correct resolution of abbreviations.
• Fixed abbreviation(for:) to use the correct daylight saving flag when computing the abbreviation for a given date.

Test improvements:

• Expanded and corrected tests in TestTimeZone to cover invalid abbreviations, valid abbreviation mapping, and proper handling of unknown timezones, ensuring the new logic is exercised and validated. [1] [2]Thank you for contributing to the Skip project! Please use this space to describe your change and add any labels (bug, enhancement, documentation, etc.) to help categorize your contribution.

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Generated this PR summary
Used it to fix the core issue, I experienced and then use the for to validate issue do not persists anymore.
Added tests

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[marcprux]

Rather than hardwiring this, could we build it dynamically by getting all the system TimeZone.getAvailableIDs() and then calling tz.getDisplayName(false, TimeZone.SHORT) on each of them?