[Android] Fix a11y set semantic focus (#1782)

* Add SemanticExtensions SetFocus and Announce

* Add Windows Announce implementation

* Update based on feedback

* Fix SetSemanticFocus for Android

* Revert order of usings to clean up diff

Co-authored-by: Brandon Minnick <13558917+brminnick@users.noreply.github.com>
Co-authored-by: Javier Suárez <javiersuarezruiz@hotmail.com>
Co-authored-by: Gerald Versluis <gerald.versluis@microsoft.com>

src/CommunityToolkit/Xamarin.CommunityToolkit/Extensions/Semantic/SemanticExtensions.android.cs

@@ -17,7 +17,7 @@ static void PlatformSetSemanticFocus(this VisualElement element)
  if (androidView is not AView view)
  throw new NullReferenceException("Can't access view");
 
- view.SendAccessibilityEvent(EventTypes.ViewFocused);
+ view.SendAccessibilityEvent((EventTypes)(int)WindowsChange.AccessibilityFocused);
  }
 
  static void PlatformAnnounce(string text)
@@ -36,4 +36,4 @@ static void PlatformAnnounce(string text)
  manager.SendAccessibilityEvent(announcement);
  }
  }
-}
+}