cmake: Autogenerate most of the .qrc resource files

With the CMake support from the previous commit, resource files
can now be autogenerated. Do this for almost all resources;
the hicolor one is special because it uses aliases, and the i18n
one requires more work that is going to be added in a follow-up
commit.

Combine several of the previous resources (e.g. different icon sets)
to reduce complexity. This wasn't possible previously due to the
various configuration-specific combinations, but can now be done
dynamically by extending the glob patterns accordingly.