[Feature] WebSocket over HTTP/2 (h2+h2c)

[hyperxpro]

Expected behavior

Currently, WebSockets only work over HTTP/1.1 in Netty, not on HTTP/2.

Actual behavior

We should make WebSocket work with HTTP/2 also.

Netty version

4.1

[KingMob]

RFC 8441 is still in "proposed" status in 2023.

It's an interesting idea to support old ws-using clients, and I was contemplating it for Aleph, but how many people want this? HTTP/2 eliminated much of the value of Websockets, and offers better socket utilization via multiplexing, so I suspect 99% of those who would have used have just gone to H2 streaming.