Anti-alias rounded borders on overflow: hidden views

Summary:
When a view is rendered with a combination of `overflow: hidden` and `borderRadius: >0`, the `ReactViewGroup` would apply the border radius using Canvas `clipPath`. In Android graphics, clipPath is not an anti-aliased operation and caused aliasing artifacts.

Changing the method to a bitmask using the `PorterDuff` method results in the same functionality, but with hardware accelerated antialiasing.

https://github.com/facebook/react-native/issues/24486

Changelog:
[Android][Change] - Views with overflow: hidden and borderRadius: >0 now render anti-aliased borders.

Reviewed By: javache

Differential Revision: D38914878

fbshipit-source-id: 45ac7e4aece7a76c4216412175e49d3d73b6f391

ReactAndroid/src/main/java/com/facebook/react/config/ReactFeatureFlags.java

@@ -144,4 +144,10 @@ public class ReactFeatureFlags {
 
   /** Temporary flag to allow execution of mount items up to 15ms earlier than normal. */
   public static boolean enableEarlyScheduledMountItemExecution = false;
+
+  /**
+   * Use a bitmap mask instead of clipPath for rounding corners so that they are antialiased in
+   * Android
+   */
+  public static boolean antiAliasRoundedOverflowCorners = false;
 }