[FEATURE] Make group coordinator configurable

[BewareMyPower]

Is your feature request related to a problem? Please describe. KoP's group coordinator was implemented from the very beginning. Kafka has introduced many optimizations for the group coordinator since that time. In addition, since the code is migrated from Scala in a very directly way, the code style is not good.

Describe the solution you'd like Add some common interfaces, and then implement these interfaces for current implementation. ThenMake the group coordinator configurable. After that, we can work on a completely new implementation of group coordinator while users can choose the original implementation.