We previously called bootstrap without the cache callbacks set up
which meant it prompted you for you password once for each of the
three keys it fished out of SSSS. Instead, display the same dialog
we display from the verify toast.
Also, in the case where you hadn't verified yet, the button didn't
do anything at all, so make it trigger a verification & change the
caption appropriately.
Add a state to reflect when cross signing is set up but SSSS isn't
(ie. user hasn't yet set up backup / set a passphrase).
