"Start Tails" should perform "Unlock"

Many people were not clicking “Unlock” before clicking “Start Tails” when activating the persistent storage. We should make “Start Tails” perform the same action as “Unlock” before starting the session.

Feature Branch: greeter:feature/revamp_phase1

Parent Task: #10812 (closed)

Original created by @alant on 10824 (Redmine)