Change MySQL database schema contract to support separate parsing and processing phase

The currrent hacky implementation uses synthetic RAW event to pass the the DDL into the MySQL database schema and then another schema change event is emitted.
The result is convoluted logic that needs indirect calls to consumer to process it conditionally.

In the new implentation we just expose methods that parse the DDL that creates typed schema change events and then the processing is the same as with other connectors.