This PR changes the ErrorWriter to be more lenient with classifying
protocols. Errors codecs are agnostic to the codec used. Therefore we
avoid checking the codec in classifying the request. IsSupported will
return true for an unknown codec which allows the server to encode a
better error message to the client. If not supported a 415 error response
could be used to match gRPC server like handling. If not supported and
trying to write an error the ErrorWriter will default to connects unary
encoding.