CNDB-13031: change Descriptor#fileFor to use the same file system as Descriptor#directory

[jasonstack]

No description provided.

[github-actions]

Checklist before you submit for review

• Make sure there is a PR in the CNDB project updating the Converged Cassandra version
• Use NoSpamLogger for log lines that may appear frequently in the logs
• Verify test results on Butler
• Test coverage for new/modified code is > 80%
• Proper code formatting
• Proper title for each commit staring with the project-issue number, like CNDB-1234
• Each commit has a meaningful description
• Each commit is not very long and contains related changes
• Renames, moves and reformatting are in distinct commits

[eolivelli]

please add unit tests about this method, it is easy to forget edge cases or introduce regressions in the future

we can probably have a static method that does the path handling, so that doing unit tests is easier

[jasonstack]

added basic unit test in cc. I will add more in CNDB side with remote file system

[sonarqubecloud]

Quality Gate failed

Failed conditions
57.1% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud

[cassci-bot]

✔️ Build ds-cassandra-pr-gate/PR-1613 approved by Butler

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Approved by Butler
See build details here

[jasonstack]

There is new approach in CNDB without relying parent directory's file system. Will close this PR as won't fix.