[libadwaita] (20 commits) ...stylesheet: Use recolorable half-transparent borders

[Alexander Mikhaylenko <alexm src gnome org>]

Summary of changes:

  bb657d8... stylesheet: Drop an unused variable (*)
  4f63b27... stylesheet: Remove alt border color (*)
  5035066... stylesheet: Stop using $borders_color for overshoot (*)
  1f13876... stylesheet: Replace solid-csd border with an inset shadow (*)
  05c180a... stylesheet: Stop using $dark_fill for notebook hover (*)
  7362e3e... stylesheet: Make dark_fill not depend on border color (*)
  8094893... stylesheet: Remove insensitive_borders_color (*)
  a93e1c5... stylesheet: Increase opacity on HC trough colors (*)
  3fe0d30... stylesheet: Remove $treeview_borders_color (*)
  c0ed244... stylesheet: Use regular $borders_color for separators (*)
  e9146ab... stylesheet: Fix legacy file chooser dialog border (*)
  4646b08... stylesheet: Simplify entry border (*)
  7947946... stylesheet: Use regular $borders_color for lists (*)
  8db67cf... stylesheet: Remove a few redundant &s (*)
  dd5f178... stylesheet: Stop using $borders_color for HC switches (*)
  9ec3854... stylesheet: Replace scrollbar border with an inset box-shad (*)
  5225f5d... stylesheet: Use box-shadow instead of border for toolbars (*)
  8bdb26e... stylesheet: Overhaul header bar and tab bar borders (*)
  43d1689... stylesheet: Add background-clip: padding-box where we use b (*)
  1463f38... stylesheet: Use recolorable half-transparent borders (*)

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