Deliver schema events to table topics

Which use case/requirement will be addressed by the proposed feature?

Just like the implementation of TRUNCATE event(https://issues.redhat.com/browse/DBZ-5610), ALTER events will be useful for any replication tool that uses the Debezium library.  When this event is available in the table topic a sink connector can use this event to apply the changes in the destination(Destination database, Data lake). Its extremely inconvenient and adds extra overhead to read the DDL of Alter from the schema changes topic. 

The other drawback with the schema changes topic is that it cannot be read by the sink connector as its not in the SinkRecord format. 

Implementation ideas (optional)

Similar to truncate, the suggestion is to add a new 'op' : 'a' which will cover all Alter operations. 

Also skipped.operations docs and config code should be extended with alter support . By Default it can be excluded.

Proposal to implement this for MySQL.

It will be useful when the raw DDL is also included in the event.

cc: ccranfor@redhat.com , jpechane