fix(rocksdb): retain Topling OLAP handles

[contrueCT]

Purpose of the PR

Topling's standalone OLAP property clear still drops and recreates the same column family. The previously reported real-JNI reproduction completes the clear task, then aborts during normal shutdown. This change clears the selected table while retaining its CF handle.

Addresses the OLAP clear/close item already tracked in #3242 and the original review. The release checklist stays open. Existing Topling and recovery PRs were checked; the merged runtime integration and snapshot-recovery fix #3293 do not cover this clear path.

Main Changes

• Clear the selected OLAP table in its owning database under the store write lock.
• Retain Topling CF handles and discard the clearing thread's pending batch before committing the clear; leave other threads' leases untouched.
• Preserve the standard RocksDB drop/create path.
• Adapt OLAP test fixtures to the shared AtomicReference owner introduced by merged fix(rocksdb): make snapshot restore retryable #3293.

Verifying these changes

• Trivial rework / code cleanup without any test coverage. (No Need)
• RocksDBSessionsTest: 28 tests pass on Java 17 after rebasing onto master 87a06a9b, with no failures/errors/skips. New tests cover retained handle identity, repeated clears, pending writes outside the stored range and in an empty table, independent OLAP routing, other-table preservation, reuse and close/reopen reads.
• Whole-repository Java 17 clean compilation, editorconfig formatting and git diff --check pass.

These tests run the Topling Java branch with the real standard RocksDB JNI. The same handle-preservation regression fails against the original master adapter. Actual Topling JNI and its reported shutdown abort were not rerun on this macOS arm64 host; current-head Linux native qualification remains necessary.

Does this PR potentially affect the following parts?

• Dependencies
• Modify configurations
• The public API
• Other affects: standalone Topling OLAP clear and native handle lifecycle
• Nope

Documentation Status

• Doc - TODO
• Doc - Done: docs/storage-lifecycle.md documents OLAP clear, handle retention and pending-write handling.
• Doc - No Need

[codecov]

Codecov Report

❌ Patch coverage is 0% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 41.71%. Comparing base (87a06a9) to head (34cc360).

Files with missing lines	Patch %	Lines
.../hugegraph/backend/store/rocksdb/RocksDBStore.java	0.00%	16 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3299      +/-   ##
============================================
- Coverage     41.92%   41.71%   -0.22%     
+ Complexity     7101     7037      -64     
============================================
  Files           770      762       -8     
  Lines         67320    67066     -254     
  Branches       9042     9022      -20     
============================================
- Hits          28226    27974     -252     
- Misses        35879    35880       +1     
+ Partials       3215     3212       -3     

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