ddl: avoid commit conflicts when updating/delete from mysql.tidb_ddl_reorg. (#38738)

[ti-chi-bot]

This is an automated cherry-pick of #38738

What problem does this PR solve?

Issue Number: close #38669, #24427

Problem Summary:

Root cause of the issue is that in HandleDDLJobTable it will

1. start a new transaction
2. call runReorgJob for reorganization work, which can update mysql.tidb_ddl_reorg table in a new transaction, for 'savepoints' in case of crash, so it can continue instead of having to restart from the beginning.
3. when runReorgJob returns it will delete the job from mysql.tidb_ddl_reorg and commit the transaction started in 1) and if 2) did update the same table, this is where the commit conflict will occur, resulting in updates to reorg_meta will not be committed and the warnings and other updates will be lost.

What is changed and how it works?

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-chi-bot]

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[ti-chi-bot]

@ti-chi-bot: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
idc-jenkins-ci-tidb/unit-test	921a1e8	link	true	/test unit-test
idc-jenkins-ci-tidb/check_dev	921a1e8	link	true	/test check-dev
idc-jenkins-ci-tidb/build	921a1e8	link	true	/test build
idc-jenkins-ci-tidb/check_dev_2	921a1e8	link	true	/test check-dev2
idc-jenkins-ci-tidb/mysql-test	921a1e8	link	true	/test mysql-test

Full PR test history. Your PR dashboard.

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