fix(material/slide-toggle): move unthemable tokens to theme mixin

Though these tokens are not currently affected by the theme, in the
future they will be affected by the design system used for theming (M2
or M3)

BREAKING CHANGE:
There are new styles emitted by mat.slide-toggle-theme that are not
emitted by any of: mat.slide-toggle-color, mat.slide-toggle-typography,
mat.slide-toggle-density. If you rely on the partial mixins only and don't
call mat.slide-toggle-theme, you can add mat.slide-toggle-base to get the
missing styles.

src/material/_index.scss

@@ -119,7 +119,8 @@ list-density, list-base;
 @forward './sidenav/sidenav-theme' as sidenav-* show sidenav-theme, sidenav-color,
   sidenav-typography, sidenav-density, sidenav-base;
 @forward './slide-toggle/slide-toggle-theme' as slide-toggle-* show
-  slide-toggle-theme, slide-toggle-color, slide-toggle-typography, slide-toggle-density;
+  slide-toggle-theme, slide-toggle-color, slide-toggle-typography, slide-toggle-density,
+  slide-toggle-base;
 @forward './slider/slider-theme' as slider-* show slider-theme, slider-color, slider-typography,
   slider-density, slider-base;
 @forward './snack-bar/snack-bar-theme' as snack-bar-* show snack-bar-theme, snack-bar-color,

src/material/slide-toggle/_slide-toggle-theme.scss

@@ -8,6 +8,12 @@
 @use '../core/tokens/m2/mat/slide-toggle' as m2-mat-slide-toggle;
 @use '../core/tokens/token-utils';
 
+@mixin base($theme) {
+  .mdc-switch {
+    @include mdc-switch-theme.theme(m2-mdc-switch.get-unthemable-tokens());
+  }
+}
+
 @mixin color($theme) {
   $is-dark: inspection.get-theme-type($theme) == dark;
   $mdc-switch-color-tokens: m2-mdc-switch.get-color-tokens($theme);
@@ -62,6 +68,7 @@
 
 @mixin theme($theme) {
   @include theming.private-check-duplicate-theme-styles($theme, 'mat-slide-toggle') {
+    @include base($theme);
     @if inspection.theme-has($theme, color) {
       @include color($theme);
     }

src/material/slide-toggle/slide-toggle.scss

@@ -38,9 +38,6 @@
     &:disabled .mdc-switch__shadow {
       box-shadow: var(--mdc-switch-disabled-handle-elevation-shadow);
     }
-
-    // Add default values for MDC switch tokens that aren't outputted by the theming API
-    @include mdc-switch-theme.theme(m2-mdc-switch.get-unthemable-tokens());
   }