general: Add accent colors
Adds accent color API to AdwStyleManager. Also adds a few color utilities.
Includes !812 (closed) !810 (merged)
There are a few major issues to sort out:
- Accent colors (and follow-system-accent) don't seem to be propagating correctly
- Even with follow-system-accent, for some reason the accent doesn't actually update when changing AdwSettings
Note that if you set follow-system-accent
to TRUE in the constructor, ADW_DEBUG_ACCENT_COLOR
works properly.
I've also not tested the portal impl yet.