tails-greeter: better administration password UI
Originally created by Tails on #5594 (Redmine)
update_passphrase_ui dynamic warning
That is, add to the greeter’s admin password and confirmation entry process the same kind of UX than the one used in t-p-s to choose a passphrase: can’t be empty, must enter twice the same passphrase, etc.
Parent Task: #8230 (closed)