*: add a reference count for StmtCtx (#39368)

[ti-chi-bot]

This is an automated cherry-pick of #39368

What problem does this PR solve?

Issue Number: close #27725

Problem Summary:

What is changed and how it works?

Check List

Tests

• Manual test (add detailed scripts or steps below)
  Using commit: 17e6297
  run

select 1;
select sleep(3);
select 1;
select 1;

Before this commit, tidb-server will panic.
After this commit, tidb-server run successfully.

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]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• CbcWestwolf
• wshwsh12

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

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

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[CbcWestwolf]

/run-unit-test

[CbcWestwolf]

/run-unit-test

[CbcWestwolf]

/retest-required

[wshwsh12]

/merge

[ti-chi-bot]

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

Commit hash: 20083f7