Persistence preset: screen locking password

I’m using tor with a persisted volume. If I set the screen lock password and reboot the screen lock password isn’t persisted.

Proposed design for a persistent password:

In the persistence configuration
================================

Add an option for a persistent password.

In the screen locking dialog
============================

Add an option to persist the password.

In Tails Greeter
================

If persistence unlocked after [Start Tails]
-------------------------------------------

- If admin password is the same as persistent password:

  Don't ask anything

- If admin password is different than persistent password:

  Ask to choose between two alternatives:

    * Ignore the persistent password
      Use the administration password for administration and unlocking the screen

    * Reset persistent password

If persistence unlocked before [Start Tails] (optional)
-------------------------------------------------------

- If persistence unlocked + persistent password:

  Display alternate layout (and explain why):

    [ ] Enable administration access

    [Reset persistent password]

- If persistence unlocked + persistent password feature + no persistent password (yet)

  Display original layout with an option to persist password:

    Set password: [               ]
    Confirm:      [               ]

    [ ] Persist this password

Related issues

• Related to #16998
• Related to #17136

Original created by @Gaff on 15641 (Redmine)