fix(kvclient): fix region merging would block the progress of resolveLock (#3062)

[ti-chi-bot]

This is an automated cherry-pick of #3062

What problem does this PR solve?

fix the bug that region merging would block the progress of resolveLock when tidb tx end abnormally and remain some prewrite lock in region. Close #3061 #2867

What is changed and how it works?

(1) When meet a fallback resolvedTs event, we send it to resolveLock thread instead of ignoring it so that resolve lock logic can trigger;
(2) Fallback resolvedTs event will also increase the penalty which will trigger resolve lock eventually.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
  Ref to the step in issue TiCDC does not resolve lock in time #2867

Related changes

• Need to cherry-pick to the release branch

Release note

fix the bug that fallback resolvedTs event  will block the progress of resolve lock when occur region merging

[ti-chi-bot]

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[amyangfei]

/merge

[ti-chi-bot]

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

Commit hash: 3c88d48

[ti-chi-bot]

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[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (release-5.1@af3f009). Click here to learn what that means.
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❗ Current head 122b1ad differs from pull request most recent head 80b27e5. Consider uploading reports for the commit 80b27e5 to get more accurate results

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[amyangfei]

/run-kafka-tests