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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[ti-chi-bot]

@ti-chi-bot: This cherry pick PR is for a release branch and has not yet been approved by release team.
Adding the do-not-merge/cherry-pick-not-approved label.

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[amyangfei]

/merge

[amyangfei]

/merge

[amyangfei]

/run-kafka-tests