compositor: add icc_profile weston.ini option for outputs

This adds "icc_profile" key support in [output] sections for backends
headless, x11, wayland, and drm, and also for remoted and pipewire
outputs FWIW. On the other hand, RDP-backend does not use output
sections from weston.ini, and fbdev-backend does not deserve anything
new (it wouldn't support color management anyway due to no GL-renderer).

This allows one to configure an ICC v2 or v4 file to be used as an
output profile. However, color-lcms does not actually use output
profiles yet, so trying this will fail until support is implemented.

The parent_winsys_profile argument is reserved for using the color
profile from a parent window system where applicable, if nothing else is
set in weston.ini. None of the nested backends provide an output color
profile yet. It is more of a reminder of a missing feature than a
serious implementation.

Note: cms-static Weston plugin uses the exact same weston.ini key for
loading VCGT from ICC profiles. If "color-management" option is set to
false, this new use of "icc_profile" is disabled and the old behavior
with cms-static is kept.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

man/weston.ini.man

@@ -545,6 +545,14 @@ An integer, 1 by default, typically configured as 2 or higher when needed,
 denoting the scaling multiplier for the output.
 .RE
 .TP 7
+.BI "icc_profile=" file
+If option
+.B color-management
+is true, load the given ICC file as the output color profile. This works only
+on DRM, headless, wayland, and x11 backends, and for remoting and pipewire
+outputs.
+.RE
+.TP 7
 .BI "seat=" name
 The logical seat name that this output should be associated with. If this
 is set then the seat's input will be confined to the output that has the seat