[To dev/1.3] Preserve query memory registrations during stale fragment cleanup

[JackieTien97]

Description

Backport #18834 to dev/1.3 (cherry-picked from b0b96f6).

A delayed fragment cleanup can delete a replacement query-memory registration, causing MemoryPool.free() to fail when buffered results are consumed. Check that the outer entry still references the map being cleaned up before removing it, under the existing registration lock.

Preserve all five regression tests from the original PR, including the deterministic concurrent cleanup test. The only backport adaptation is resolving the test import difference with dev/1.3.

Validation

• Clean DataNode reactor build and focused unit tests passed: MemoryPoolTest (27 tests), SharedTsBlockQueueTest (2 tests); no failures, errors, or skips.

  mvn clean test -pl iotdb-core/datanode -am \
    -Dtest=MemoryPoolTest,SharedTsBlockQueueTest \
    -Dsurefire.failIfNoSpecifiedTests=false -DfailIfNoTests=false

• Spotless and git diff --check passed.

Checklist

• Self-reviewed concurrent registration and deregistration.
• Preserved the explanation of the identity check.
• Backported and ran the regression tests.

Key changed classes

• MemoryPool
• MemoryPoolTest

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 45.43%. Comparing base (3f9a0de) to head (4f2243a).

Additional details and impacted files

@@              Coverage Diff              @@
##             dev/1.3   #18840      +/-   ##
=============================================
+ Coverage      45.40%   45.43%   +0.02%     
  Complexity       198      198              
=============================================
  Files           3667     3667              
  Lines         251095   251096       +1     
  Branches       31088    31089       +1     
=============================================
+ Hits          114013   114076      +63     
+ Misses        137082   137020      -62     

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