[FLINK-35243][cdc] Support table schema change events & PreSchema backfill

[yuxiqian]

This PR closes FLINK-35243:

• Supports AlterColumnCommentEvent, AlterTableCommentEvent, DropTableEvent, RenameTableEvent, and TruncateTableEvent in pipeline framework
• Adds SchemaChangeEventWithPreSchema interface, allowing SchemaRegistry backfilling schema before change payload
• Fixed MySQL pipeline source doesn't capture ALTER TABLE ... MODIFY COLUMN DDL
• Adds corresponding test cases

[yuxiqian]

@PatrickRen @ruanhang1993 PTAL

[melin]

DropTableEvent TruncateTableEvent can be closed. Sometimes, tables cannot be deleted synchronously.

[yuxiqian]

DropTableEvent TruncateTableEvent can be closed. Sometimes, tables cannot be deleted synchronously.

Hi @melin, thanks for your comments. It's a common use case to apply some "safe" schema change events (like AddColumnEvent) and ignore "dangerous" events (like Truncate / Drop tables). So we're designing a new feature allowing users to configure schema change behaviour for each type of schema change events in FLINK-35242. Also, we're trying to expose interfaces allowing Sink connectors to report their supported kind of schema change events.

This PR is still in early draft stage, so feel free to leave your comments if you have any other concerns.