fix(material/core): disable strong focus indicators in high contrast mode (#24120)

Most components have special handling for high contrast mode which can cause double focus indication when strong focus indication is disabled.

These changes remove the strong focus indicators if such a case is detected.

Fixes #24097.

(cherry picked from commit 040ef57)

Author: crisbeto

src/material-experimental/mdc-helpers/_focus-indicators.scss

@@ -28,6 +28,10 @@
     pointer-events: none;
     border: $border-width $border-style transparent;
     border-radius: $border-radius;
+
+    .cdk-high-contrast-active & {
+      display: none;
+    }
   }
 
   // By default, all focus indicators are flush with the bounding box of their

src/material/core/focus-indicators/_focus-indicators.scss

@@ -28,6 +28,10 @@
     pointer-events: none;
     border: $border-width $border-style transparent;
     border-radius: $border-radius;
+
+    .cdk-high-contrast-active & {
+      display: none;
+    }
   }
 
   // By default, all focus indicators are flush with the bounding box of their