Support binary logging of wire protocol data

[tweidema]

Describe the solution you'd like

In Release 2.x I would like to see support for binary logging, maybe based on https://github.com/grpc/grpc/blob/master/doc/binary-logging.md . Should include both message- and meta-data.
My use-case is a low-overhead, but complete log of traffic server-side, to/from clients, primarily for use in supportcases. Logging the binary protocol data should be low-overhead in the call-path and take up less storage (as opposed to logging deserialized/parsed messages), and it doesn't matter (to me) if it then takes time to search/parse the data when there is a need for it.
Another usecase would be documenting/replaying integration testruns.
I've looked in the source-code, and Sources/GRPCCore/Call/Server/Internal/ServerRPCExecutor.swift seems to be the place for it, at least for incoming traffic.

Describe alternatives you've considered

Logging deserialized/parsed data from single methods or from a serverInterceptor if possible.

[glbrntt]

This would certainly be nice to have. I'm not sure how we should add this at the moment though. For one, we don't have (and don't want) a protobuf dependency in this package; we also don't have complete information (peer information and some metadata is provided at the transport layer, for example). One approach might be to define a binary logger API which different transport implementations emit appropriate events into and have a decoupled backend which you can consume the events from (i.e. turn the binary log events into protobuf messages).

Logging deserialized/parsed data from single methods or from a serverInterceptor if possible.

You should be able to get most of the info with this approach but you'd need to reserialize the messages which isn't something we'd like to do in a general purpose solution as it can be pretty costly.