Mark classes of package uimanager as @nullsafe (#43162)

Summary:
Pull Request resolved: #43162

All these classes are NullSafe, let's mark them as NullSafe(Local) to ensure lint detect errors in the future

bypass-github-export-checks

changelog: [internal] internal

Reviewed By: javache

Differential Revision: D54027181

fbshipit-source-id: af9f022d36a2e60788d6790525736d1b6cfdf6fa

Author: mdvacca

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/PixelUtil.java

@@ -9,8 +9,10 @@
 
 import android.util.DisplayMetrics;
 import android.util.TypedValue;
+import com.facebook.infer.annotation.Nullsafe;
 
 /** Android dp to pixel manipulation */
+@Nullsafe(Nullsafe.Mode.LOCAL)
 public class PixelUtil {
 
   /** Convert from DIP to PX */

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/PointerEvents.java

@@ -7,12 +7,14 @@
 
 package com.facebook.react.uimanager;
 
+import com.facebook.infer.annotation.Nullsafe;
 import java.util.Locale;
 
 /**
  * Possible values for pointer events that a view and its descendants should receive. See
  * https://developer.mozilla.org/en-US/docs/Web/CSS/pointer-events for more info.
  */
+@Nullsafe(Nullsafe.Mode.LOCAL)
 public enum PointerEvents {
 
   /** Neither the container nor its children receive events. */

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/ReactClippingViewGroupHelper.java

@@ -10,12 +10,14 @@
 import android.graphics.Rect;
 import android.view.View;
 import android.view.ViewParent;
+import com.facebook.infer.annotation.Nullsafe;
 import javax.annotation.concurrent.NotThreadSafe;
 
 /**
  * Provides implementation of common tasks for view and it's view manager supporting property {@code
  * removeClippedSubviews}.
  */
+@Nullsafe(Nullsafe.Mode.LOCAL)
 @NotThreadSafe
 public class ReactClippingViewGroupHelper {