fix(material/form-field): 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.form-field-theme that are not
emitted by any of: mat.form-field-color, mat.form-field-typography,
mat.form-field-density. If you rely on the partial mixins only and don't
call mat.form-field-theme, you can add mat.form-field-base to get the
missing styles.

Author: mmalerba

src/material/_index.scss

@@ -94,7 +94,7 @@
 @forward './expansion/expansion-theme' as expansion-* show expansion-theme, expansion-color,
   expansion-typography, expansion-density;
 @forward './form-field/form-field-theme' as form-field-* show form-field-theme,
-  form-field-color, form-field-typography, form-field-density;
+  form-field-color, form-field-typography, form-field-density, form-field-base;
 @forward './grid-list/grid-list-theme' as grid-list-* show grid-list-theme, grid-list-color,
   grid-list-typography, grid-list-density;
 @forward './icon/icon-theme' as icon-* show icon-theme, icon-color, icon-typography, icon-density;

src/material/form-field/_form-field-theme.scss

@@ -11,6 +11,20 @@
 @use '../core/tokens/token-utils';
 @use './form-field-density';
 
+@mixin base($theme) {
+  @include sass-utils.current-selector-or-root() {
+    @include token-utils.create-token-values(
+        tokens-mdc-filled-text-field.$prefix,
+        tokens-mdc-filled-text-field.get-unthemable-tokens());
+    @include token-utils.create-token-values(
+        tokens-mdc-outlined-text-field.$prefix,
+        tokens-mdc-outlined-text-field.get-unthemable-tokens());
+    @include token-utils.create-token-values(
+        tokens-mat-form-field.$prefix,
+        tokens-mat-form-field.get-unthemable-tokens());
+  }
+}
+
 @mixin color($theme) {
   @include sass-utils.current-selector-or-root() {
     @include mdc-filled-text-field-theme.theme(
@@ -57,6 +71,7 @@
 
 @mixin theme($theme) {
   @include theming.private-check-duplicate-theme-styles($theme, 'mat-form-field') {
+    @include base($theme);
     @if inspection.theme-has($theme, color) {
       @include color($theme);
     }

src/material/form-field/form-field.scss

@@ -15,7 +15,6 @@
 @use '../core/tokens/m2/mat/form-field' as tokens-mat-form-field;
 @use '../core/tokens/m2/mdc/filled-text-field' as tokens-mdc-filled-text-field;
 @use '../core/tokens/m2/mdc/outlined-text-field' as tokens-mdc-outlined-text-field;
-@use '../core/style/sass-utils';
 @use './form-field-sizing';
 @use './form-field-subscript';
 @use './form-field-focus-overlay';
@@ -44,24 +43,12 @@
 @include mdc-custom-properties.configure(
   $emit-fallback-values: false, $emit-fallback-vars: false) {
 
-  @include sass-utils.current-selector-or-root() {
-    @include token-utils.create-token-values(
-      tokens-mat-form-field.$prefix,
-      tokens-mat-form-field.get-unthemable-tokens());
-  }
-
   .mdc-text-field--filled {
-    @include token-utils.create-token-values(
-      tokens-mdc-filled-text-field.$prefix,
-      tokens-mdc-filled-text-field.get-unthemable-tokens());
     @include mdc-filled-text-field-theme.theme-styles(
       tokens-mdc-filled-text-field.get-token-slots());
   }
 
   .mdc-text-field--outlined {
-    @include token-utils.create-token-values(
-      tokens-mdc-outlined-text-field.$prefix,
-      tokens-mdc-outlined-text-field.get-unthemable-tokens());
     @include mdc-outlined-text-field-theme.theme-styles(
       tokens-mdc-outlined-text-field.get-token-slots());
   }