[Fix][torch.compile] fix unique_filepath

[ZJY0516]

Purpose

unique_filepath was introduced in #24542 but the corresponding implementation was not included in the final commit.

CC @ProExpertProg

Test Plan

Test Result

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Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
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• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[gemini-code-assist]

Code Review

This pull request adds the unique_filepath utility function, which was intended to be included in a previous PR. The implementation finds a unique file path by incrementing an integer suffix. My review identifies a critical Time-of-Check to Time-of-Use (TOCTOU) race condition in the current implementation. I've suggested a fix that uses an atomic file creation operation to prevent potential file conflicts and data corruption in multi-threaded or multi-process environments. Additionally, I recommend adding unit tests for this new utility to ensure its correctness and handle edge cases, as they appear to be missing.