raftstore-v2: init persisted_tablet_index on startup

[tabokie]

What is changed and how it works?

Issue Number: Ref #12842

What's Changed:

- Initialize `persisted_apply_index` on startup.

Related changes

pingcap/tidb#45517

#15332

Check List

Tests

• Unit test

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• SpadeA-Tang
• tonyxuqqi

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[tabokie]

/merge

[ti-chi-bot]

@tabokie: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

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

Commit hash: f7cf15b

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.1: #15477.