Output device changes aren't working in 2.6's echo test when artifical delay
is on due to the fact that the feedback audio is being played via the WebAudio
context rather the the HTMLMediaElement. Since output device change works
via HTMLMediaElement's setSinkId, it's basically a no-op.
This commit fixes the issue by piping the AudioContext destination
through the main audio element rather than using WebAudio directly for
playback. An additional stub media element (muted) is added to circumvent one
of Chrome's WebAudio issue.
The alternative would be to use AudioContext's setSinkId, but it isn't
supported by Firefox (setSinkId enabled) and Chrome < 110.
This should work with FF (setSinkId enabled) and a wide array of Chromium
versions.
1ada7dc57e