executor, planner: fix collation for hash join building (#23770)

[ti-srebot]

cherry-pick #23770 to release-4.0
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# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/23812

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---

What problem does this PR solve?

Issue Number: close #23693

Problem Summary:
outerHashKeys[i].GetType().Charset, outerHashKeys[i].GetType().Collate = chs, coll

collate is modified here, when building the merge join, the collate is wrong.

What is changed and how it works?

Correct the collation in the executor.

Related changes

• Need to cherry-pick to the release branch

Check List

Tests

• Unit test

Side effects

Release note

• fix collation for hash join building

[ti-srebot]

/run-all-tests

[ti-srebot]

@wjhuang2016 you're already a collaborator in bot's repo.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• qw4990
• winoros

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[wjhuang2016]

/merge

[ti-chi-bot]

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

Commit hash: 0e1cab6

[qw4990]

/merge

[ti-chi-bot]

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

Commit hash: cd22796

[zhouqiang-cl]

/merge

[ti-chi-bot]

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

Commit hash: 82a6f9b

[ti-chi-bot]

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