Fix device selection in pre-join screen for Element Call video rooms (#9321)

* Fix device selection in pre-join screen for Element Call video rooms

As per https://github.com/vector-im/element-call/pull/609

* Update unit test

* Lint

* Hold a media stream while we enumerate device so we can do so reliably.

This means we can remove the device fallback labels.

* i18n

* Remove unnecessary useState

* Fix fetching video devices when video muted

* Actually fix preview stream code

* Fix unit test now fallback is no longer a thing

* Test changing devices

src/i18n/strings/en_EN.json

@@ -1047,11 +1047,9 @@
     "Hint: Begin your message with <code>//</code> to start it with a slash.": "Hint: Begin your message with <code>//</code> to start it with a slash.",
     "Send as message": "Send as message",
     "Audio devices": "Audio devices",
-    "Audio input %(n)s": "Audio input %(n)s",
     "Mute microphone": "Mute microphone",
     "Unmute microphone": "Unmute microphone",
     "Video devices": "Video devices",
-    "Video input %(n)s": "Video input %(n)s",
     "Turn off camera": "Turn off camera",
     "Turn on camera": "Turn on camera",
     "Join": "Join",