executor: fix data race because of using shared KV requests (#61376)

[ti-chi-bot]

This is an automated cherry-pick of #61376

What problem does this PR solve?

Issue Number: close #60175

Problem Summary:

What changed and how does it work?

The different coprocessor iterator should run on different KV requests, the share usage can cause data race.

Check List

Tests

• [x] Unit test
• [ ] Integration test
• [ ] Manual test (add detailed scripts or steps below)
• [ ] No need to test

  • [ ] I checked and no code files have been changed.

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[bot]]

Codecov Report

Attention: Patch coverage is 80.85106% with 9 lines in your changes missing coverage. Please review.

Please upload report for BASE (release-8.5@f43a133). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.5     #61416   +/-   ##
================================================
  Coverage               ?   57.2067%           
================================================
  Files                  ?       1771           
  Lines                  ?     629940           
  Branches               ?          0           
================================================
  Hits                   ?     360368           
  Misses                 ?     245441           
  Partials               ?      24131           

Flag	Coverage Δ
integration	37.0841% <80.8510%> (?)
unit	72.8238% <80.8510%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	52.9278% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	52.4813% <0.0000%> (?)

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[you06]

/retest

[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: cfzjywxk, zyguan

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The pull request process is described here

Needs approval from an approver in each of these files:

• ~~OWNERS~~ [cfzjywxk,zyguan]
• ~~pkg/distsql/OWNERS~~ [cfzjywxk]

Approvers can indicate their approval by writing /approve in a comment Approvers can cancel approval by writing /approve cancel in a comment

[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2025-06-18 06:38:03.373435908 +0000 UTC m=+253736.096614891: :ballot_box_with_check: agreed by cfzjywxk.
• 2025-06-18 11:43:33.260489461 +0000 UTC m=+272065.983668442: :ballot_box_with_check: agreed by zyguan.

[you06]

/retest

[you06]

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[you06]

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[you06]

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[you06]

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