cdc: add changefeed epoch to prevent unexpected state (#8268)

[ti-chi-bot]

This is an automated cherry-pick of #8268

What problem does this PR solve?

Issue Number: close #7657
Also close #8242

What is changed and how it works?

Add changefeed epoch, so we can distinguish messages after changefeed restart.

Check List

Tests

• Unit test

Questions

Will it cause performance regression or break compatibility?

No

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

No

Release note

Fix an issue that may cause data lost or checkpoint stuck when changefeed restarting.

[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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