util: fix memory leak in chunk allocator (#40989)

[ti-chi-bot]

This is an automated cherry-pick of #40989

What problem does this PR solve?

Issue Number: close #40987

Problem Summary:

What is changed and how it works?

Unlink the reference to the chunk for freeColumns.allocColumns and freeColumns.freeColumns.

Check List

Tests

• Unit test

• Integration test

• Manual test (add detailed scripts or steps below)
  

• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

Fix the potential memory leak when enable tidb_enable_reuse_chunk.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• XuHuaiyu
• hawkingrei

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[XuHuaiyu]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 526cd88

[ti-chi-bot]

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