restore: split between tables

[YuJuncen]

What problem does this PR solve?

Issue Number: close #42924

Problem Summary:
When restoring tables, for optimization, we are not going to split between tables:
(Referencing #27240)

before：
--|-------t1 data-------|-----|---t2 data-------|
after: 
----------t1 data-------|---------t2 data-------|

Legends:
'|' the split point
'-' the key space

This works fine as long as we are restoring tables sequentially and restoring tables after we finish splitting. However, for now, in some scenarios:

1. t2 starts its restoration, importing file to the very left region.
2. t1 starts its restoration too, and split region from left to right -- the table may be huge and take a long time to split the regions.
3. Newly split regions will be born from the very right region of t1, i.e. the very left region of t2. Which means... this region's epoch would change frequently, which probably blocks the import of t2.

What is changed and how it works?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
  We detected this problem in an internal cluster, where v7.0.0 BR consistently fails, and with this PR we can restore to the cluster.
• (Almost) No code

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

Fixed a bug that may cause BR failed to restore due to "epoch not match".

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• 3pointer
• Leavrth

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[YuJuncen]

/merge

[ti-chi-bot]

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

Commit hash: 748fb23

[hawkingrei]

/retest

[hawkingrei]

/retest

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-5.4: #43164.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.1: #43165.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #43166.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-5.3: #43167.