Align RoQ and SDP-RoQ drafts (in SDP-RoQ)

[SpencerDawkins]

This issue is the counterpart to Issue 224 in thertp-over-quic-draft Github repo.

For background, see the June 2024 AVTCORE virtual interim meeting notes for both RoQ and SDP-RoQ sessions.

This issue is intended to capture what is not part of the current RoQ specification, and is not specifically tied to SDP for RoQ.

As a starting point, this would include options for opening, and for reusing, a QUIC connection for RoQ.

These options include (at least)

• manual configuration of an endpoint,
• reuse of a QUIC connection that was used for SDP,
• use of the "roq" APLN defined in the RoQ specification, and
• using SDP to open and reuse a QUIC connection, similarly to the way RTP over TCP uses SDP to open and reuse TCP connections.

This issue will likely grow before it shrinks!