statistics: kill in time when to run topnStatsMergeWorker and improve memory (#45765)

[ti-chi-bot]

This is an automated cherry-pick of #45765

What problem does this PR solve?

Issue Number: close #45706

Problem Summary:

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

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (release-6.5@df3fa99). Click here to learn what that means.
The diff coverage is n/a.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-6.5     #45767   +/-   ##
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  Coverage               ?   73.6491%           
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  Files                  ?       1083           
  Lines                  ?     347116           
  Branches               ?          0           
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  Hits                   ?     255648           
  Misses                 ?      75033           
  Partials               ?      16435           

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hi-rustin, qw4990

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• OWNERS [hi-rustin,qw4990]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2023-08-10 06:59:34.579297036 +0000 UTC m=+182339.128313007: ☑️ agreed by hi-rustin.
• 2023-08-10 07:05:55.229931352 +0000 UTC m=+182719.778947328: ☑️ agreed by qw4990.