Change some optional dependencies from being optional to being mandatory
or being mandatory but behind on-by-default cmake flags. Eg: instead of
only compiling Wayland support if we find the appropriate libraries, we
always require the libraries unless the user specifies WITH_WAYLAND=OFF.
Optional libraries are hard to discover by packagers (since they don't
see an error once we add them) and create lots of possible build flavors
with a different features that can confuse users.
Add the necessary bits for XDG activation to work
Move the code for launching the settings from the daemon to the respective processes so that we don't need to pass activation tokens over another process boundary
