syncer: support start from empty gtid config (#5340)

[ti-chi-bot]

This is an automated cherry-pick of #5340

What problem does this PR solve?

Issue Number: close #3731

What is changed and how it works?

mariadb could use 0-0-0 as empty gtid config

• support user to use uuid:0 as mysql empty gtid config

Check List

Tests

• Integration test
• Manual test (mariadb)

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation
• Need to update key monitor metrics in both TiCDC document and official document

Release note

Support start an incremental task with nil MySQL GTID set.

[ti-chi-bot]

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