feat(material/theming): Open up new APIs to access theme values

This PR opens up the following Sass APIs used to access theme values:
- `get-theme-version`: Gets the version of the theme object
- `get-theme-type`: Gets the type of theme (light or dark)
- `get-theme-color`: Gets a color from the theme
- `get-theme-typography`: Gets a typography value from the theme
- `get-theme-density`: Gets the density scale from the theme
- `theme-has`: Checks if the theme has information for the given theming
  system

src/material-experimental/column-resize/_column-resize-theme.scss

@@ -1,9 +1,9 @@
 @use '@angular/material' as mat;
 
 @mixin color($theme) {
-  $non-resizable-hover-divider: mat.private-get-theme-color($theme, foreground, divider);
-  $resizable-hover-divider: mat.private-get-theme-color($theme, primary, 600);
-  $resizable-active-divider: mat.private-get-theme-color($theme, primary, 600);
+  $non-resizable-hover-divider: mat.get-theme-color($theme, foreground, divider);
+  $resizable-hover-divider: mat.get-theme-color($theme, primary, 600);
+  $resizable-active-divider: mat.get-theme-color($theme, primary, 600);
 
   // TODO: these styles don't really belong in the `color` part of the theme.
   // We should figure out a better place for them.
@@ -136,13 +136,13 @@
 
 @mixin theme($theme) {
   @include mat.private-check-duplicate-theme-styles($theme, 'mat-column-resize') {
-    @if mat.private-theme-has($theme, color) {
+    @if mat.theme-has($theme, color) {
       @include color($theme);
     }
-    @if mat.private-theme-has($theme, density) {
+    @if mat.theme-has($theme, density) {
       @include density($theme);
     }
-    @if mat.private-theme-has($theme, typography) {
+    @if mat.theme-has($theme, typography) {
       @include typography($theme);
     }
   }

src/material-experimental/popover-edit/_popover-edit-theme.scss

@@ -6,7 +6,7 @@
 }
 
 @mixin color($theme) {
-  $background-color: mat.private-get-theme-color($theme, background, 'card');
+  $background-color: mat.get-theme-color($theme, background, 'card');
 
   // TODO: these structural styles don't belong in the `color` part of a theme.
   // We should figure out a better place for them.
@@ -42,7 +42,7 @@
     position: relative;
 
     &::after {
-      background-color: mat.private-get-theme-color($theme, primary);
+      background-color: mat.get-theme-color($theme, primary);
       bottom: 0;
       content: '';
       height: 2px;
@@ -78,7 +78,7 @@
   .mat-edit-pane {
     @include mat.private-theme-elevation(2, $theme);
     background: $background-color;
-    color: mat.private-get-theme-color($theme, foreground, text);
+    color: mat.get-theme-color($theme, foreground, text);
     display: block;
     padding: 16px 24px;
 
@@ -144,8 +144,8 @@
 
 @mixin typography($theme) {
   [mat-edit-title] {
-    font: mat.private-get-theme-typography($theme, headline-6, font);
-    letter-spacing: mat.private-get-theme-typography($theme, headline-6, letter-spacing);
+    font: mat.get-theme-typography($theme, headline-6, font);
+    letter-spacing: mat.get-theme-typography($theme, headline-6, letter-spacing);
   }
 }
 
@@ -154,13 +154,13 @@
 
 @mixin theme($theme) {
   @include mat.private-check-duplicate-theme-styles($theme, 'mat-popover-edit') {
-    @if mat.private-theme-has($theme, color) {
+    @if mat.theme-has($theme, color) {
       @include color($theme);
     }
-    @if mat.private-theme-has($theme, density) {
+    @if mat.theme-has($theme, density) {
       @include density($theme);
     }
-    @if mat.private-theme-has($theme, typography) {
+    @if mat.theme-has($theme, typography) {
       @include typography($theme);
     }
   }

src/material/_index.scss

@@ -142,7 +142,6 @@ list-density, list-base;
   $private-mdc-base-styles-query, $private-mdc-base-styles-without-animation-query,
   $private-mdc-theme-styles-query, $private-mdc-typography-styles-query;
 
-// New theming APIs, currently in development:
-@forward './core/theming/inspection' as private-* show private-get-theme-version,
-  private-get-theme-type, private-get-theme-color, private-get-theme-typography,
-  private-get-theme-density, private-theme-has;
+// New theming APIs:
+@forward './core/theming/inspection' show get-theme-version, get-theme-type, get-theme-color,
+  get-theme-typography, get-theme-density, theme-has;