Add tests to watch behavior in both protocols (http and websocket)
against all 3 media types. Adopt the
`application/vnd.kubernetes.protobuf;stream=watch` media type for the
content that comes back from a watch call so that it can be
distinguished from a Status result.
Add a recognizer that is capable of sniffing content type from data by
asking each serializer to try to decode - this is for a "universal
decoder/deserializer" which can be used by client logic.
Add codec factory, which provides the core primitives for content type
negotiation. Codec factories depend only on schemes, serializers, and
groupversion pairs.