Implements `WebSocket` over http/2. This requires a conformant http/2
server supporting the extended connect protocol.
Passes approximately 100 new WPT tests (mostly `?wpt_flags=h2` versions
of existing websockets APIs).
This is implemented as a fallback when http/1.1 fails, so a server that
supports both h1 and h2 WebSockets will still end up on the http/1.1
upgrade path.
The patch also cleas up the websockets handshake to split it up into
http, https+http1 and https+http2, making it a little less intertwined.
This uncovered a likely bug in the WPT test server:
https://github.com/web-platform-tests/wpt/issues/42896
This is a rewrite of the `Deno.serve` API to live on top of hyper
1.0-rc3. The code should be more maintainable long-term, and avoids some
of the slower mpsc patterns that made the older code less efficient than
it could have been.
Missing features:
- `upgradeHttp` and `upgradeHttpRaw` (`upgradeWebSocket` is available,
however).
- Automatic compression is unavailable on responses.
