fix(tianmu): hotfix corruption in ValueOrNull under multi-thread

[RingsC]

Summary about this PR

In multi-thread aggregation, ExpressionColumn will occur double free due to without protection. Thread A will do ValueOrNull::operator ==, but in thread B, it will try to free it. Therefore, it leads to instance crash.

Issue Number: close #1855

Tests Check List

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Changelog

• New Feature
• Bug Fix
• Performance Improvement
• Build/Testing/CI/CD
• Documentation
• Not for changelog (changelog entry is not required)

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features

[mergify]

Thanks for the contribution!
I have applied any labels matching special text in your PR Changelog.

Please review the labels and make any necessary changes.

[codecov]

Codecov Report

Patch coverage: 63.63% and project coverage change: -5.00 ⚠️

Comparison is base (7d03695) 60.25% compared to head (99bb989) 55.25%.

❗ Current head 99bb989 differs from pull request most recent head c3a35ac. Consider uploading reports for the commit c3a35ac to get more accurate results

Additional details and impacted files

@@                 Coverage Diff                 @@
##           stonedb-5.7-dev    #1869      +/-   ##
===================================================
- Coverage            60.25%   55.25%   -5.00%     
===================================================
  Files                 1837     2031     +194     
  Lines               380678   431538   +50860     
===================================================
+ Hits                229371   238461    +9090     
- Misses              151307   193077   +41770     

Impacted Files	Coverage Δ
storage/tianmu/handler/ha_tianmu.cpp	51.54% <ø> (ø)
storage/tianmu/optimizer/aggregation_algorithm.cpp	73.25% <ø> (+16.96%)	⬆️
storage/tianmu/optimizer/aggregator_basic.h	63.45% <ø> (+1.69%)	⬆️
storage/tianmu/optimizer/group_table.cpp	78.36% <0.00%> (+10.02%)	⬆️
storage/tianmu/vc/column_share.h	100.00% <ø> (ø)
storage/tianmu/vc/expr_column.cpp	70.19% <ø> (ø)
storage/tianmu/optimizer/aggregator_basic.cpp	32.49% <40.00%> (+<0.01%)	⬆️
storage/tianmu/core/value_or_null.cpp	68.11% <100.00%> (+0.51%)	⬆️
storage/tianmu/core/value_or_null.h	89.74% <100.00%> (+0.26%)	⬆️

... and 269 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.

[zhongshengstoneatom]

LGTM