Make HighContrastInverse a dark variant

Make HighContrastInverse available as the dark variant of HighContrast,
in addition to being a standalone theme. This regularizes our theme
variants, and doesn't hurt.

gtk/gen-gtk-gresources-xml.py

@@ -49,9 +49,10 @@ for f in get_files('theme/Adwaita/assets', '.svg'):
 
 xml += '''
     <file>theme/HighContrast/gtk.css</file>
-    <file alias='theme/HighContrastInverse/gtk.css'>theme/HighContrast/gtk-inverse.css</file>
+    <file>theme/HighContrast/gtk-dark.css</file>
+    <file alias='theme/HighContrastInverse/gtk.css'>theme/HighContrast/gtk-dark.css</file>
     <file>theme/HighContrast/HighContrast.css</file>
-    <file>theme/HighContrast/HighContrast-inverse.css</file>
+    <file>theme/HighContrast/HighContrast-dark.css</file>
 '''
 
 for f in get_files('theme/HighContrast/assets', '.png'):

gtk/theme/HighContrast/gtk-dark.css

@@ -1 +1 @@
-@import url("resource:///org/gtk/libgtk/theme/HighContrast/HighContrast-inverse.css");
+@import url("resource:///org/gtk/libgtk/theme/HighContrast/HighContrast-dark.css");

gtk/theme/HighContrast/meson.build

@@ -3,7 +3,7 @@ hc_scss_files = files([
 ])
 
 hc_theme_variants = [
-  'inverse',
+  'dark',
 ]
 
 hc_theme_deps = [