ddl: remove useless fields in CopContextBase

[lcwangchao]

What problem does this PR solve?

Issue Number: close #53388

What changed and how does it work?

remove useless fields in CopContextBase

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

[tiprow]

Hi @lcwangchao. Thanks for your PR.

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[YangKeao]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-05-31 10:05:21.465100949 +0000 UTC m=+3030075.222236517: ☑️ agreed by tangenta.
• 2024-05-31 10:20:44.526541132 +0000 UTC m=+3030998.283676705: ☑️ agreed by YangKeao.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.8542%. Comparing base (b137425) to head (56caca0).
Report is 2 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #53721        +/-   ##
================================================
+ Coverage   72.5762%   73.8542%   +1.2780%     
================================================
  Files          1506       1506                
  Lines        430947     431065       +118     
================================================
+ Hits         312765     318360      +5595     
+ Misses        98878      93147      -5731     
- Partials      19304      19558       +254     

Flag	Coverage Δ
integration	47.2578% <100.0000%> (?)
unit	71.4375% <100.0000%> (-0.1333%)	⬇️

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

Components	Coverage Δ
dumpling	53.9957% <ø> (ø)
parser	∅ <ø> (∅)
br	42.1011% <ø> (+0.2667%)	⬆️