Device dehydration: detect and handle when user has a dehydrated device for which we don't have the key #29579
Description
If dehydration gets set up on a different device, and we don't have the key, detect this condition, and prompt the user for the SSSS key so that we can get the dehydration key.
This is similar to the "Key storage out of sync" toast, and we can probably add on to that.