[libadwaita] (16 commits) ...doc: Mention the new accent color in migration guide

[Adrien Plazas <aplazas src gnome org>]

Summary of changes:

  83f6741... stylesheet: Rename selected_bg/fg_color to accent_color/tex (*)
  20b081b... stylesheet: Drop an unused color (*)
  8238a3f... stylesheet: Rework filled button states again (*)
  f4a246e... stylesheet: Use lighter hover for fills as well (*)
  8727138... stylesheet: Make sure switch and progress bar recoloring wo (*)
  f5199c6... stylesheet: Ensure menus are recolorable (*)
  2d8d40f... stylesheet: Ensure status page is recolorable (*)
  7e0de41... stylesheet: Don't add background to message dialog headers (*)
  46c3775... stylesheet: Unify accent, destructive, success, warning, er (*)
  4723344... stylesheet: Expose all the overridable colors publicly (*)
  de9d728... stylesheet: Consistently use gtkalpha() (*)
  108c35f... stylesheet: Add and use gtkmix() (*)
  cc50abf... stylesheet: Implement recoloring for accent and a few other (*)
  c5d480c... stylesheet: Use a more contrasty accent for foreground (*)
  9ac415d... stylesheet: Add the .accent style class (*)
  b4723e4... doc: Mention the new accent color in migration guide (*)

(*) This commit already existed in another branch; no separate mail sent