Add generalized support for conditional updates

https://github.com/Aiven-Open/jdbc-connector-for-apache-kafka/pull/375 adds support to update rows in a database only when a specific condition is met. This currently works for UPSERT and SQL Server dialect, but it could be supported for UPDATE and other dialects.

This feature is interesting and important -- a (strictly?) increasing field like a timestamp can be used to enforce idempotency where we can safely replay events and arrive at the same final state.