executor: release memory usage of task in indexJoin/indexHashJoin (#34418)

[ti-srebot]

cherry-pick #34418 to release-6.0
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/34476

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/tidb.git pr/34476:release-6.0-b1379a61b5b5

---

What problem does this PR solve?

Issue Number: close #34417

Problem Summary:
Test tpch q3,q7,q8. The tracked memory is more than actual memory usage...
The root cause is that the tracked memory is not reset after the task is processed.

What is changed and how it works?

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.

None

[ti-chi-bot]

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[ti-srebot]

/run-all-tests

[ti-srebot]

@wshwsh12 you're already a collaborator in bot's repo.

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/6db90e0d833b33d9693c789a0e79899971800e79