Update go2rtc, simplify manual stream, and support audio for MSE & WebRTC (#4391)

* Update go2rtc to rc3

* Simplify ffmpeg / audio conversions

* Set ffmpeg bin location

* Manually set video as copied

* Run go2rtc with env vars

* Remove manual ffmpeg declaration

* Enable force_audio by default

* Fix test

docker/rootfs/etc/services.d/go2rtc/run

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/with-contenv bash
 
 # https://gist.github.com/mohanpedala/1e2ff5661761d3abd0385e8223e16425?permalink_comment_id=3945021
 set -euo pipefail