refactor: stale file test package migration [GKE-GCSFuse Test migration]

[PranjalC100]

Description

This PR includes changes to migrate stale file test package to use common config file. This common config will be used by both GCSFuse binary and GCSFuse csi driver tests.

Changes include:

refactoring to use config file by test methods.
changes are made in a backward compatible way so tests can run with both config file and flags. This will be cleaned up in future PRs after the migration is complete.
Migration of stale file package so it can use config file.

Link to the issue in case of a bug fix.

b/445952888

Testing details

1. Manual - Manually tested with config file for both cases when mounted directory is set and not set. Also validated that the tests work without config file.
2. Unit tests - NA
3. Integration tests - via KOKORO

Any backward incompatible change? If so, please explain.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 0.00%. Comparing base (f48d62d) to head (8058db5).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #3884       +/-   ##
==========================================
- Coverage   83.29%       0   -83.30%     
==========================================
  Files         153       0      -153     
  Lines       18624       0    -18624     
==========================================
- Hits        15513       0    -15513     
+ Misses       2542       0     -2542     
+ Partials      569       0      -569     

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