Call-progress tones

This is a small collection/tracker issue for [Call-progress tones](https://en.wikipedia.org/wiki/Call-progress_tone).

I used Element Android for a call today, and I noticed that some features (such as a ringing tone) are missing, so here are some of those;

- [ ] Ringing Tone (mentioned in #1687, but reiterated for explicitness' sake), used when calling the other party (regardless if the VoIP connection is established)
- [ ] Busy Tone
- *Not sure where to use this one, i'm inclined to say "use it as a hangup signal, as Wikipedia says:*

> Typically, the disconnect tone is a few cycles of the reorder or busy tone (e.g. in US), or between five and fifteen seconds of the Number Unobtainable tone (e.g. in UK).
- *I'm also inclined to say "use this as a connection failure tone", to play when VoIP call establishment is showing to fail, or the TURN server is not availible.*
- [ ] Disconnect Tone, (only if above tone isn't used) maybe something like [iPhone's quick hangup beeps](https://www.youtube.com/watch?v=GzKBjRGeSXQ)