[WIP]Implement reproducible out/ folder contents across different filesystem layouts

[rahat2134]

This PR addresses issue #3660 by making the out/ folder contents more reproducible and filesystem layout agnostic. These changes allow for re-using the out/ folder as a build cache between different machines, supporting both coarse-grained (e.g., zip file transfer) and fine-grained (via Bazel remote cache protocol) caching strategies.

Key Changes:

• Updated PathRef to normalize paths relative to workspace, Coursier cache, and home directory
• Implemented NonDeterministicFiles to handle non-deterministic file content
• Updated JsonFormatters to use the new path normalization methods
• Added integration test ReproducibleOutTest to verify reproducibility
• Updated build.mill in the integration test to define the necessary project structure

Reproducibility is achieved by:

1. Normalizing paths in serialized PathRefs
2. Handling non-deterministic files (e.g., mill-profile.json, worker JSONs)
3. Zeroing out modification times for zip and jar files

Testing:

• Added new integration test ReproducibleOutTest
• Existing tests have been updated and pass

Documentation:

• Updated relevant comments in the code

Performance Impact:

• Initial testing shows minimal impact on build times, but more extensive performance testing may be needed for large projects