executor: prevent sending cop request for show columns (#36613)

[ti-srebot]

cherry-pick #36613 to release-6.2
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/36630

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/tidb.git pr/36630:release-6.2-e39ef4cae80f

---

What problem does this PR solve?

Issue Number: close #36426, #36496

What is changed and how it works?

This PR prevents running the executor when executing SHOW COLUMNS or reading INFORMATION_SCHEMA.COLUMNS.

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

[ti-srebot]

/run-all-tests

[ti-srebot]

@tangenta you're already a collaborator in bot's repo.

[sre-bot]

Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/3cf2c49828251bab1185a0c7b62f6aff7b6c2c9b

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• lcwangchao
• xiongjiwei

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[lcwangchao]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 2731687

[hawkingrei]

/run-unit-test

[ti-chi-bot]

@ti-srebot: Your PR was out of date, I have automatically updated it for you.

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