Instead of having to manually stub packages that should not be
downloaded we instead automatically stub all packages (except a small
list of whitelisted ones). Tests can re-introduce the real package by
using the `realPkgs` module argument.
* screen-locker: Make xautolock optional, reorganize options
xautolock isn't really needed to trigger xss-lock on the basis of time
since the built-in screensaver functionality of X serves as one of the
event sources for xss-lock. Keeping it around and defaulting to
"enabled" to avoid unexpected breakage.
Also shuffled around the options to submodules for xss-lock and
xautolock to get rid of prefixes in option names and to make
enableDetectSleep a bit clearer.
* screen-locker: update maintainership
* tests/screen-locker: Stub i3lock and xss-lock
* screen-locker: add package options for xss-lock and xautolock
