[CommonCore] Fix issue with legacy keychain on macOS.

[juan-arias]

Proposed changes

This pull request addresses an issue with the legacy keychain on macOS by updating logging and error handling in the MSIDMacKeychainTokenCache implementation. Instead of creating unimplemented errors for certain methods, the code now logs informational messages and returns early, which should improve clarity when these methods are called in unsupported contexts.

Key changes:

Keychain error handling and logging improvements:

• Updated jsonObjectsWithKey:serializer:context:error: and saveJsonObject:serializer:key:context:error: in MSIDMacKeychainTokenCache.m to log informational messages instead of generating unimplemented errors, and to return nil or NO as appropriate.

Type of change

• Feature work
• Bug fix
• Documentation
• Engineering change
• Test
• Logging/Telemetry

Risk

• High – Errors could cause MAJOR regression of many scenarios. (Example: new large features or high level infrastructure changes)
• Medium – Errors could cause regression of 1 or more scenarios. (Example: somewhat complex bug fixes, small new features)
• Small – No issues are expected. (Example: Very small bug fixes, string changes, or configuration settings changes)

Additional information

[juan-arias]

These changes were released manually, they will be merged to dev in #1625