Enable non-sender RTT from negotiated rcvr-rtt; report video RTT

Drive RRTR/DLRR enablement from the negotiated receive_non_sender_rtt
flag (set by the SDP layer from either rtcp-xr:rcvr-rtt or the legacy
rtcp-fb rrtr) instead of HasRrtr, for both the audio and video receive
channels. Enablement uses SetReceiveNonSenderRttEnabled on each receive
channel: receive streams can be created before the receive parameters
are finalized (e.g. a recvonly endpoint creates them while processing
the offer), so the value cannot reliably be set at stream construction
and must be applied via the setter, as the voice channel already does.

Also surfaces the computed video non-sender RTT into
RTCRemoteOutboundRtpStreamStats (GetNonSenderRttStats ->
VideoReceiveStream2::Stats -> VideoReceiverInfo), resolving the
long-standing TODO(bugs.webrtc.org/12529).

Bug: webrtc:516205747
Change-Id: I01da1c79389e4818ca8023c2f248e32b1b84aa2c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/479241
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#48157}