txn: change lock into put record for unique index key lock (#25730)

[ti-srebot]

cherry-pick #25730 to release-5.1
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/26225

After apply modifications, you can push your change to this PR via:

git push git@github.com:ti-srebot/tidb.git pr/26225:release-5.1-3a5f434aad40

---

What problem does this PR solve?

Issue Number:
Related to #25659

Problem Summary:
Since #21229, all the unique index keys will be locked if they are used in the for update read access path. The for update read with point get on non-clusetered unique index keys may leave many LOCK records which affect the performance a lot.

What is changed and how it works?

What's Changed:
Change the LOCK record into PUT when the for update read is used for point/batch point get unqiue index read.
Record the original index value into memory buffer so that the record will be PUT.

How it Works:

Related changes

• Need to cherry-pick to the release branch

Check List

Tests

• Unit test

Side effects

• Put more data into storage when the unique key index is written as the value part contains the handle value, when the point/batch point get for update read are used.

Release note

• Change the lock record into put record for the index keys using point/batch point get for update read.

[ti-srebot]

/run-all-tests

[ti-srebot]

@cfzjywxk please accept the invitation then you can push to the cherry-pick pull requests.
https://github.com/ti-srebot/tidb/invitations

[sticnarf]

LGTM

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• sticnarf
• youjiali1995

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[you06]

LGTM

[zhouqiang-cl]

/merge

[ti-chi-bot]

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

Commit hash: 0b2f506

[AilinKid]

/merge

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