store/tikv: increase batch split region limit (#24508)

[nolouch]

Signed-off-by: nolouch [email protected]

What problem does this PR solve?

Ref: #22969
Problem Summary:
Splitting and Scattering at the same time will cause multiple conflicts on the same region.

What is changed and how it works?

How it Works: increase the split regions' limit.

Check List

Tests

• Make the time consuming of split table more stable

I have run multiple times  to split 4000 regions, and the time is stale about `1m30s`
split single sql result: [map[SCATTER_FINISH_RATIO:1 TOTAL_SPLIT_REGION:2001]]
split all sql run total cost: 1m28.908304306s
split all sql run success!!!

Release note

• Increasing the split region limit makes the split table and pre split more stable

[ti-chi-bot]

@nolouch: Adding the "do-not-merge/release-note-label-needed" label because no release-note block was detected, please follow our release note process to remove it.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• disksing
• lhy1024

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[lhy1024]

/merge

[ti-chi-bot]

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

Commit hash: 03df897

[nolouch]

/merge

[nolouch]

/run-unit-test

[nolouch]

/merge