Submission of WebTransport API to WICG (and refactoring of the WebRTC-QUIC API)

Feedback on the WebRTC-QUIC P2P API has come from developers who are primarily interested in client/server use cases rather than peer-to-peer use cases involving WebRTC.  For those developers, it is desirable to avoid dependencies on ICE.

As a result, a specification focusing on client/server use cases has been created.  Since this specification supports client/server use cases including support for HTTP/3 connection pooling, it has been renamed the  "WebTransport API" and has been submitted to WICG<https://discourse.wicg.io/t/webtransport-proposal/3508>.

The WebTransport explainer is here<https://github.com/pthatcherg/web-transport/blob/master/explainer.md> and the WebTransport API specification is here<https://pthatcherg.github.io/web-transport/>.

In order to avoid duplicating the content in the WebTransport API, the WebRTC-QUIC P2P API has been reworked to reference objects defined in the WebTransport API instead<https://w3c.github.io/webrtc-quic/>.   Note that there are still a few dangling references left<https://github.com/w3c/webrtc-quic/issues/127> that should be fixed soon<https://github.com/w3c/webrtc-quic/pull/128>.

Since much of the material in the former WebRTC-QUIC API now resides in the WebTransport API document, ORTC CG participants interested in the evolution of the API would be advised to join WICG where it is expected that discussion of client/server aspects will take place.

The ORTC CG will focus on P2P aspects requiring a dependency on ICE, which are defined here<https://w3c.github.io/webrtc-quic/>.