This mocks gsd-colord to enable night ligth at a given temperature. The
test then verifies that the result exactly matches that of the gamma
ramps gsd-color generated for the same temperature and ICC profile.
There are two types of profiles tested; ones with VCGT, i.e. calibrated
profiles, and ones without. These are tested as the VCGT affects how the
gamma curve looks, while the non-VCGT profiles all only rely on
the blackbody temperature to generate a gamma ramp.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2165>
gsd-color provides this API, which exposes details about the night light
state. Currently, gsd-color also turns this state into CRTC gamma
changes, but this will eventually change, and this is a preparation for
this.
The proxy isn't yet used for anything.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2164>
