Add support for Databend to act as MySQL replica

[itziklavon]

Clickhouse has this database engine:
MaterializedMySQL

currently i'm using clickhouse, and my mysql instance is on AWS RDS
however, this engine does not support AWS RDS for replication

so, the feature is couple of things actually

1. Add support for databend to act as mysql replica
2. Add support to allow replica of cloud services(AWS RDS included)

Thanks!

[sundy-li]

Ok, since the feature of MaterializedMySQL engine in ClickHouse is also from our team, we do have a plan to support it in Databend in the future.