Support read-only MySQL connection in incremental snapshot

MySQL connector's current implementation is writing updates to signal table to start incremental snapshot and open/close incremental snapshot window.

Add an option to support read-only connection:

1. Use Kafka topic to start incremental snapshot.
2. Use executed GTID set as low/high watermarks for incremental snapshot window.

Discussed in https://groups.google.com/g/debezium/c/JS3LjfE3WQo