session: use TxnCtx.InfoSchema, no matter vars.InTxn() or not (#42027)

[ti-chi-bot]

This is an automated cherry-pick of #42027

What problem does this PR solve?

Issue Number: close #41622 close #42003

Problem Summary:

What is changed and how it works?

Build plan need to use the same InfoSchema, but vars.InTxn() is false in #41622.
Relax the condition can fix issue/41622

Alternative: change all sctx.GetInfoSchema() to sessiontxn.GetTxnManager(sctx).GetTxnInfoSchema()
It involves a lot of changes and seems more fragile comparing to this single line of change.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Test with the reproduce provided by @crazycs520 in the issue.

• 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: 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 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/check_dev_2	451e9ce	link	true	/test check-dev2
idc-jenkins-ci-tidb/mysql-test	451e9ce	link	true	/test mysql-test

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