Test suite: split various checks feature
_Originally created by Tails on [#5707 (Redmine)](https://public-redmine-archive.tails.boum.org/code/issues/5707)_
As currently implemented, `checks.feature` mixes various unrelated
checks for the sole reason of improving the test suite runtime.
Unfortunately, this is deemed to result in a quickly growing bitrot
space.
Instead, the scenarii that are currently in there should be split into
functionally grouped independent features, that would share a tag
expressing that they can share a common background snapshot.
Feature Branch: test/5707-split-checks.feature
### Related issues
- [x] **Blocked by** tails/tails#6094
issue