This pulls the 3PID state management in Settings up to a single location so that
the Account and Discovery sections now work from a single list that updates
immediately.
Fixes https://github.com/vector-im/riot-web/issues/10519
Probably still not the best design but hopefully break fewer UX rules:
1. Use red to confirm delete rather than cancel and green to cancel
2. Show the action you're about to perform in the confirmation
3. Label confirmation button with the action rather than yes/no.
