fix(blink): resend signals to ensure all peers connect

[sdwoodbury]

What this PR does 📖

• refactors blink (simple_webrtc and host_media were mostly left alone). Most of the logic is now in blink_controller.rs instead of split between the blink implementation, webrtc_controller.rs (removed) and call_initiation.rs (also removed).

the new design made it easy to add the following improvements:

• when offering a call, the offer signal is resent upon failure.
• during a call, all participants announce their presence and deterministically initiate webrtc connections by comparing DIDs.

other improvements

• participants now tell the others when they are recording
• someone should be able to be offline when a call is offered, turn on the app, and join the call
• if BlinkImpl is cloned and that clone is dropped, it won't shut down the background tasks anymore.
• someone should be able to join a call and know who is muted/unmuted/recording. This is done by sending the ParticipantState in the Announce event and removing the other signals. Blink now has an event for ParticipantStateChanged.

Which issue(s) this PR fixes 🔨
Not an issue in Warp but should address the issue where, especially during a group call, not all the participants can hear each other.

Special notes for reviewers 🗒️

Additional comments 🎤

[dariusc93]

you should probably check the strong count of the reference so if its the only thing left, it can signal its waiters. Eg

if Arc::strong_count(&self.notify) == 1 {
   self.notify.notify_waiters();
}

[sdwoodbury]

notify gets cloned and passed to some tasks. I think that dropping NotifyWrapper wouldn't necessarily mean the strong count would be one. I hoped that by putting NotifyWrapper in an Arc, Drop wouldn't be called until all the Arc<NotifyWrapper>s were dropped.