ddl: check index key length when convert charset (#56964)

[ti-chi-bot]

This is an automated cherry-pick of #56964

What problem does this PR solve?

Issue Number: close #56930

Problem Summary:
Miss the check of index length.

What changed and how does it work?

Check the index length when convert to new charset.

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

[codecov]

Codecov Report

Attention: Patch coverage is 45.45455% with 12 lines in your changes missing coverage. Please review.

Please upload report for BASE (release-7.5@5a6e570). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.5     #57929   +/-   ##
================================================
  Coverage               ?   72.1559%           
================================================
  Files                  ?       1415           
  Lines                  ?     413022           
  Branches               ?          0           
================================================
  Hits                   ?     298020           
  Misses                 ?      95029           
  Partials               ?      19973           

Flag	Coverage Δ
unit	72.1559% <45.4545%> (?)

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

Components	Coverage Δ
dumpling	52.9400% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	53.5329% <0.0000%> (?)

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: fzzf678, tangenta

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• OWNERS [tangenta]
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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-12-11 05:41:20.384832758 +0000 UTC m=+417070.473635300: ☑️ agreed by fzzf678.
• 2024-12-11 05:49:07.473837316 +0000 UTC m=+417537.562639859: ☑️ agreed by tangenta.