custom-set-faces! and custom-theme-set-faces! are now drop-in
replacements for custom-set-faces and custom-theme-set-faces with one
major distinction: the latter will wait for the theme to be loaded
before applying the changes, this allows you to use theme-specific APIs
in your face definitions (like doom-color from doom-themes).
You no longer have to think about load order when using these macros.