add unit test coverage for StorageUtil

[aglinxinyuan]

Task Summary

StorageUtil (common/workflow-core/src/main/scala/org/apache/texera/amber/core/storage/util/StorageUtil.scala) provides loan-pattern wrappers (withReadLock, withWriteLock, withLock) but currently has no unit tests. Add StorageUtilSpec covering:

• Each wrapper executes the block and returns its value
• Each wrapper releases the underlying lock even when the block throws

Priority

P3 – Low

Task Type

• Testing / QA