See [discussion](https://github.com/kroxylicious/design/discussions/22)

We want to extract a kroxylicious-filter-api module with all the interfaces a Filter Author needs to build and configure a new filter.

As part of this we want to explore:
1. removing netty dependencies from KrpcFilterContext
2. introducing interfaces for DecodedRequestFrame, DecodedResponseFrame, DecodedFrame to keep netty out of the filter api if possible
3. Move KrpcFilter, KrpcFilterContext, other dependant interfaces and the generated per-message interfaces into a kroxylicious-filter-api module
4. Think about whether we can avoid a jackson dependency for loading the configuration, for example if we wanted a configuration class with a test constructor, it might be nice if we could use our own annotation to indicate which constructor to use rather than depend on Jackson.