Add buttons to restart Tails at the end of creating the Persistent Storage

Originally created by @intrigeri on #16384 (Redmine)

Mockup:

(Note the disabled Close [X] button in the title bar, if possible.)

Related to #11529: Save data to Persistence when it is created (no need to restart)
Related to #17760 (closed): Consider including a reboot icon / graphic in final step of persistence setup

Edited Jul 03, 2020 by sajolida

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