sink, ddl(ticdc): support add index ddl in downstream (#11476)

[ti-chi-bot]

This is an automated cherry-pick of #11476

What problem does this PR solve?

Issue Number: close #10682

What is changed and how it works?

• Always wait for async ddl done before executing the next normal ddl
• Note: wait indefinitely here to avoid pointless retries
• Any errors encountered will be ignored in the check, and if the add index operation in downstream is not complete at this point, TiCDC will fall back to the current master's behavior.

Check List

Tests

• Unit test
• Manual test

Questions

Will it cause performance regression or break compatibility?

Do you need to update user documentation, design documentation or monitoring documentation?

Release note

`None`.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: CharlesCheung96

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[CharlesCheung96]

/retest