Propose to delete data from a persistence feature when it is deactivated

When you deactivate a persistence feature, the corresponding data is not erased from the persistent volume. This is nothing new, but I’m realizing that this is not made clear to the user and this is a problem:

• People might believe that this data has been deleted when it is not.
• People might have bad surprises as Tails autoconnecting to networks that they had configured in the past but disabled since then.

First we should discuss whether we think that this is a problem, and its gravity. Then we can move on to proposing solutions: wiping disabled features by default, prompting the user to choose whether wiping or not, mentioning this in the documentation only, etc.

Related issues

• Related to #14544
• Has duplicate #12448 (closed)

Original created by @sajolida on 8447 (Redmine)