feat(material/core): rename theme mixin (#29857)

Author: andrewseguin

src/dev-app/theme-m3.scss

@@ -47,7 +47,7 @@ html {
   }
 
   body.demo-experimental-theme {
-    @include mat.private-experimental-theme((
+    @include mat.theme((
       color: (
         theme-type: light,
         primary: $primary,
@@ -83,7 +83,7 @@ body.demo-unicorn-dark-theme {
   }
 
   &.demo-experimental-theme {
-    @include mat.private-experimental-theme((
+    @include mat.theme((
       color: (
         theme-type: dark,
         primary: $primary,
@@ -110,7 +110,7 @@ $density-scales: (-1, -2, -3, -4, minimum, maximum);
     }
 
     body.demo-experimental-theme & {
-      @include mat.private-experimental-theme((density: $scale));
+      @include mat.theme((density: $scale));
     }
   }
 }

src/material/_index.scss

@@ -20,8 +20,7 @@
 @forward './core/tokens/m2' show m2-tokens-from-theme;
 @forward './core/tokens/m3-system' show system-level-colors,
     system-level-typography, system-level-elevation, system-level-shape,
-    system-level-motion, system-level-state;
-@forward './core/tokens/m3-system' as private-experimental-* show private-experimental-theme;
+    system-level-motion, system-level-state, theme;
 
 // Private/Internal
 @forward './core/density/private/all-density' show all-component-densities;