* add function to pause device listener
* add function to check if key backup key missing both locally and in 4s
* reset backup if backup key missing both locally and in 4s
* fixup! add function to check if key backup key missing both locally and in 4s
* Drop KEY_STORAGE_OUT_OF_SYNC_STORE in favour of checking cross-signing
Check if cross-signing needs resetting, because that seems to be what
KEY_STORAGE_OUT_OF_SYNC_STORE is actually trying to do.
* add a function for resetting key backup and waiting until it's ready
* trigger key storage out of sync toast when missing backup key locally
and fetch it when user enters their recovery key
* reset backup when needed if user forgets recovery key
* rename function as suggested in code review
aee24be1b4