capture(ticdc): fix the problem that openapi is blocked when pd is abnormal (#4788)

[ti-chi-bot]

This is an automated cherry-pick of #4788

What problem does this PR solve?

Issue Number: close #4778

What is changed and how it works?

1. Avoid holding a mutex lock in a blocking operation.
2. Add timeout control for EtcdClient get and put operations to prevent possible goroutine leak in openapi.
   
3. Remove redundant retry operations in (*openApi).forwardToOwner

Check List

Tests

• Unit test

Related changes

• Need to cherry-pick to the release branch

Release note

`Fix a bug that openapi may be stuck when pd is abnormal`

[ti-chi-bot]

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[CharlesCheung96]

Batch cherry-pick through #4533