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 24 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #500180
flatpak

00:00:44

 
  Deploy
passed #500181
review

00:00:19

passed #500182
manual
stop_review

00:00:20