fix(switch): theming issues with focus in dark theme (#11459)

Closes #8518
Fixes #11417

Author: Splaktar

src/components/switch/switch-theme.scss

@@ -9,7 +9,20 @@ md-switch.md-THEME_NAME-theme {
     background-color: '{{background-500}}';
   }
 
-  &.md-checked {
+  &.md-focused {
+    &:not(.md-checked) {
+      .md-thumb:before {
+        background-color: '{{foreground-4}}';
+      }
+    }
+    &[disabled] {
+      .md-thumb:before {
+        background-color: '{{foreground-4}}';
+      }
+    }
+  }
+
+  &.md-checked:not([disabled]) {
     .md-ink-ripple {
       color: '{{accent-color}}';
     }

src/components/switch/switch.scss

@@ -61,19 +61,13 @@ md-switch {
     }
   }
 
-  &.md-focused:not([disabled]) {
+  &.md-focused {
     .md-thumb:before {
       left: -8px;
       top: -8px;
       right: -8px;
       bottom: -8px;
     }
-
-    &:not(.md-checked) {
-      .md-thumb:before {
-        background-color: rgba(0, 0, 0, 0.12);
-      }
-    }
   }
 
   .md-label {