Handle references for exception sets in Synchronized Groups

[mirkokg]

Generate permanent references for PBXFileSystemSynchronizedExceptionSet objects, including build file and build phase exception sets. Updates tests to verify that references for exception sets are correctly converted to permanent values.

Resolves #934

Short description 📝

When creating projects with PBXFileSystemSynchronizedRootGroup objects that contain exception sets (PBXFileSystemSynchronizedBuildFileExceptionSet or PBXFileSystemSynchronizedGroupBuildPhaseMembershipExceptionSet), the exception set IDs were being written with TEMP_ prefixes instead of proper deterministic IDs.

Solution 📦

Extended the ReferenceGenerator to process exception sets when generating references for synchronized root groups. Added a new generateExceptionSetReferences method that:

1. Iterates through all exceptions in a PBXFileSystemSynchronizedRootGroup
2. Generates deterministic IDs based on the exception type:

• For PBXFileSystemSynchronizedBuildFileExceptionSet: uses the target reference as part of the identifier
• For PBXFileSystemSynchronizedGroupBuildPhaseMembershipExceptionSet: uses the build phase reference as part of the identifier

This follows the same pattern used for other object types in the reference generator.

Implementation 👩‍💻👨‍💻

• Identified that PBXFileSystemSynchronizedRootGroup.exceptions were not being processed in ReferenceGenerator
• Modified generateSynchronizedRootGroupReferences() to iterate through exception sets after fixing the root group reference
• Added generateExceptionSetReferences() method to handle reference generation for exception set objects
• Added unit tests to verify the functionality
• Verified all tests pass with the changes
• Confirmed no TEMP_ prefixes appear in generated project files