planner: fix PointGetPlan.PrunePartitions function works with non-binary collate (#62002)

[ti-chi-bot]

This is an automated cherry-pick of #62002

What problem does this PR solve?

Issue Number: close #61965, close #59827

Problem Summary:

What changed and how does it work?

Check List

Tests

• 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

[ti-chi-bot]

@Defined2014 This PR has conflicts, I have hold it.
Please resolve them or ask others to resolve them, then comment /unhold to remove the hold label.

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 4 lines in your changes missing coverage. Please review.

Please upload report for BASE (release-8.5@fbff775). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.5     #62082   +/-   ##
================================================
  Coverage               ?   57.4328%           
================================================
  Files                  ?       1771           
  Lines                  ?     632685           
  Branches               ?          0           
================================================
  Hits                   ?     363369           
  Misses                 ?     245352           
  Partials               ?      23964           

Flag	Coverage Δ
integration	37.5481% <80.0000%> (?)
unit	73.1188% <80.0000%> (?)

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	52.4483% <0.0000%> (?)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AilinKid, hawkingrei

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [AilinKid,hawkingrei]
• pkg/planner/OWNERS [AilinKid,hawkingrei]

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]

[LGTM Timeline notifier]

Timeline:

• 2025-06-30 06:30:07.548045274 +0000 UTC m=+1290060.271224255: ☑️ agreed by AilinKid.
• 2025-06-30 06:30:29.028706914 +0000 UTC m=+1290081.751885881: ☑️ agreed by hawkingrei.

[Defined2014]

/retest