color-selection: Use libportal for Wayland suport

Greatly simplify our color selection code by
using libportal instead of implementing it manually.

Fixes #38
3 jobs for wip/christopherdavis/libportal-picker in 1 minute and 17 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
failed #500176
flatpak

00:01:17

 
  Deploy
skipped #500177
review
skipped #500178
allowed to fail manual
stop_review
 
Name Stage Failure
failed
flatpak Test

A full log can be found at /builds/World/gcolor3/_build/meson-logs/meson-log.txt
Uploading artifacts...
WARNING: gcolor3-nightly.flatpak: no matching files
WARNING: repo/: no matching files
_build/meson-logs/meson-log.txt: found 1 matching files

WARNING: _build/meson-logs/testlog.txt: no matching files
Uploading artifacts to coordinator... ok
id=500176 responseStatus=201 Created token=mx9jf-xn
ERROR: Job failed: exit code 1