Reset current_memory_tracker when WNEstablishDisaggTaskHandler finished.

[JinheLin]

What problem does this PR solve?

Issue Number: close #8173

Problem Summary:

1. In WNEstablishDisaggTaskHandler::execute, a ProcessListElement object will be created and sets current_memory_tracker to its memory_tracker member in constructor. And current_memory_tracker will be reset in the destructor of ProcessListElement.

2. However, objects of ProcessListElement are created in threads of WNEstablishDisaggTaskPool, but destructed in threads of GRPC because it will be destructed with object of WNEstablishDisaggTaskHandler (handler -> dag_context -> process_list_entry).

3. This result in current_memory_tracker of threads of WNEstablishDisaggTaskPool is not reset after task finished and other tasks may continue to use this memory tracker, although it may have already been destructed.

What is changed and how it works?

• Reset current_memory_tracker after tasks of WNEstablishDisaggTaskPool finished.

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

None

[JinheLin]

/run-all-tests

[guo-shaoge]

Suggested change

	[db_context = db_context, &task_id, &request, &response, deadline = grpc_context->deadline()]() {
	[&db_context, &task_id, &request, &response, deadline = grpc_context->deadline()]() {

maybe better?

[JinheLin]

'db_context' in capture list does not name a variable

Lambda could not capture structured binding in C++17.

Ref: https://stackoverflow.com/questions/46114214/lambda-implicit-capture-fails-with-variable-declared-from-structured-binding

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: guo-shaoge, JaySon-Huang

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Details

Needs approval from an approver in each of these files:

• OWNERS [JaySon-Huang,guo-shaoge]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-10-09 08:16:27.899663522 +0000 UTC m=+1040185.486773652: ☑️ agreed by JaySon-Huang.
• 2023-10-09 08:20:11.770941297 +0000 UTC m=+1040409.358051443: ☑️ agreed by guo-shaoge.

[JinheLin]

/run-all-tests

[JaySon-Huang]

/cherry-pick release-7.4

[ti-chi-bot]

@JaySon-Huang: new pull request created to branch release-7.4: #8175.

Details

In response to this:

/cherry-pick release-7.4

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