refactor(multiple): Stop exposing theme-from-token sass functions

We still need these functions, but we don't need to expose them since
we're shelving `mat.theme` for now

Author: mmalerba

src/material/BUILD.bazel

@@ -23,7 +23,6 @@ sass_library(
     name = "sass_lib",
     srcs = [
         "_index.scss",
-        "_token-theming.scss",
     ],
     deps = [
         "//src/material/core:core_scss_lib",

src/material/_index.scss

@@ -38,7 +38,6 @@
 @forward './core/style/button-common' as private-button-common-*;
 // The form field density mixin needs to be exposed, because the paginator depends on it.
 @forward './form-field/form-field-theme' as private-form-field-* show private-form-field-density;
-@forward './token-theming' as private-apply-*;
 @forward './core/style/sass-utils' as private-*;
 
 // Structural

src/material/_token-theming.scss

@@ -89,7 +89,7 @@
   }
 }
 
-@mixin theme-from-tokens($tokens) {
+@mixin _theme-from-tokens($tokens) {
   @if ($tokens != ()) {
     $elevated-card-tokens: map.get($tokens, tokens-mdc-elevated-card.$prefix);
     // Work around a bug in MDC where the elevation is not resolved to an actual shadow value.

src/material/card/_card-theme.scss

@@ -97,7 +97,7 @@
   }
 }
 
-@mixin theme-from-tokens($tokens) {
+@mixin _theme-from-tokens($tokens) {
   @if ($tokens != ()) {
     // TODO(mmalerba): Some of the theme styles above are not represented in terms of tokens,
     //   so this mixin is currently incomplete.