executor: store correct plan hint in statements_summary when log level is 'debug' (#22219)

[ti-srebot]

cherry-pick #22219 to release-4.0
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr 22293

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

git push git@github.com:ti-srebot/tidb.git pr/22293:ti-srebot:release-4.0-fe9d3161fa7a

---

What problem does this PR solve?

Issue Number: close #22203

Problem Summary:

Baseline capture does not work as expected.

What is changed and how it works?

What's Changed:

Make sure planHint is correctly set in statements_summary when the log level is debug or the tidb_slow_log_threshold is set to 0.

How it Works:

getEncodedPlan may be called in LogSlowQuery which would only generate encoded plan(i.e, with no plan hint), we should make sure the consequent getEncodedPlan call in SummaryStmt can generate plan hint then.

Related changes

• Need to cherry-pick to the release branch

Check List

Tests

• Unit test
• Manual test: set log level to debug, or tidb_slow_log_threshold to 0 and execute the queries in the issue, binding is successfully captured.

Side effects

N/A

Release note

• Make baseline capture work when log level is 'debug'

[ti-srebot]

/run-all-tests

[ti-srebot]

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

[eurekaka]

/run-tics-test
/run-sqllogic-test-2

[qw4990]

LGTM

[Reminiscent]

LGTM