These were still missing on my Sid system.

Some distros don't have GNOME Disks well integrated or some non-Debian
users might still prefer the command line.

Fix-committed: #16261

Earlier implementation restricted all users except root from using su.
This has been changed now. This implementation only restricts 'amnesia'
user from using su. Others users can now use su.

Merge branch 'hefee/bugfix/16186-disable-autocrypt+force-all-tests' into devel (Fix-committed: #15657, #15661, #16222)

Note: this branch actually does _not_ do anything special wrt. Autocrypt,
nor does it address #16186 (if there's anything to address there, which
is unclear at the moment).

We do need this branch merged in time before the 3.12 freeze.
There are still a few things to fix here and there but their
ETA is either after the freeze, or unknown.

refs: #15292

The follow-up fixes after the review of this branch were pushed
but not reviewed yet. Regardless, we need this branch merged
so that 3.12~rc1 can be prepared.

refs: #15999

This branch might be incomplete (left to check) and it needs a tiny bit of
polishing, but it's definitely an incremental improvement over the current
state of things: this will ensure we have a more relevant test suite
when preparing 3.12~rc1.

refs: #16004

At this point it's unclear whether there's a problem to solve
(https://redmine.tails.boum.org/code/issues/16299#note-20)
and if there's one, whether this is the best way to solve it
(https://redmine.tails.boum.org/code/issues/16299#note-19).

This reverts commit a2bb3bf0.

Merge remote-tracking branch 'origin/devel' into hefee/bugfix/16186-disable-autocrypt+force-all-tests