Fix read lock leak in disk usage statistics

[shuwenwei]

Description

Disk usage statistics acquire a resource read lock when collecting files and acquire another when registering a reader reference for scanning. After scanning, only one lock is released and the file is removed from the cleanup queue, leaving a read lock held even after the statistics utility is closed.

Register one FileReaderManager reference when collecting each closed file, and consistently release it through decreaseFileReaderReference() when skipping a file, finishing a scan, or cleaning up remaining files. Remove the duplicate reference registration before scanning. This balances reader references and resource read locks for both tree-model and table-model disk usage statistics.

Validation

• Self-reviewed acquisition, skipped-file, scan success/failure, and cleanup paths against the current FileReaderManager implementation.
• Tests were not run.

Key changed classes

• DiskUsageStatisticUtil

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 45.59%. Comparing base (eb0e3f1) to head (cefad09).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...ngine/dataregion/utils/DiskUsageStatisticUtil.java	50.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #18807      +/-   ##
============================================
- Coverage     45.59%   45.59%   -0.01%     
  Complexity      712      712              
============================================
  Files          5496     5496              
  Lines        396800   396799       -1     
  Branches      51621    51621              
============================================
- Hits         180929   180908      -21     
- Misses       215871   215891      +20     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.