planner, session: use SessionExtendedInfoSchema if snapshot isn't set (#38794)

[ti-chi-bot]

This is an automated cherry-pick of #38794

Signed-off-by: wjhuang2016 huangwenjun1997@gmail.com

What problem does this PR solve?

Issue Number: close #38791

Problem Summary:

1. Previously, we new a SessionExtendedInfoSchema in tryLockMDLAndUpdateSchemaIfNecessary(). But it doesn't change the pass-in infoSchema. The compiler/Executor may use the InfoSchema instead of SessionExtendedInfoSchema later.
2. If the schema is changed, we need to clean TableToColumnMaps.

What is changed and how it works?

1. When getting the session infoschema, new a SessionExtendedInfoSchema in GetDomainInfoSchema(). So that we don't need to new it tryLockMDLAndUpdateSchemaIfNecessary().
2. Clean TableToColumnMaps if the schema is changed.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
  Sysbench with oltp_writeonly workload on a TiDB cluster, and modify column many times, no panic occurred.
• 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.

Fix a bug that connection panic when modifying a column while doing some DML operations with MDL enabled.

[ti-chi-bot]

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[ti-chi-bot]

@ti-chi-bot: This cherry pick PR is for a release branch and has not yet been approved by release team.
Adding the do-not-merge/cherry-pick-not-approved label.

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[ti-chi-bot]

@ti-chi-bot: The following test 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/mysql-test	8a4da5c	link	true	/test mysql-test

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