Title: Add More Features of MySQL Proxy

Description:

Currently, Envoy MySQL Proxy seems only support collecting stats. Our team wants to extend MySQL Proxy, make it support more features like route, authentication, mirrors, fault like Redis Proxy.

There are already some work/proposals of supporting MySQL relevant area in the community, see blow. I wonder whether it makes sense of community to consider adding these features of MySQL Proxy.

[optional Relevant Links:]

#13551
#3501
#3502
#4975