Fix logic for mKeepActivity (#44139)

Summary:
Pull Request resolved: #44139

I added logic to make useEffect() work w/ fragment-based nav, but I mixed up some logic. Fixed it here
Changelog: [Internal]

Differential Revision: D56264138

fbshipit-source-id: b551f0cb93cb4a0291733edbd341d3508b61e392

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

@@ -771,7 +771,9 @@ public void destroy() {
     }
 
     mHasStartedCreatingInitialContext = false;
-    mCurrentActivity = null;
+    if (!mKeepActivity) {
+      mCurrentActivity = null;
+    }
 
     ResourceDrawableIdHelper.getInstance().clear();
 

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/bridge/ReactContext.java

@@ -361,6 +361,21 @@ public void onHostPause() {
   /** Should be called by the hosting Fragment in {@link Fragment#onDestroy} */
   @ThreadConfined(UI)
   public void onHostDestroy() {
+    onHostDestroyImpl();
+    mCurrentActivity = null;
+  }
+
+  @ThreadConfined(UI)
+  public void onHostDestroy(boolean keepActivity) {
+    if (!keepActivity) {
+      onHostDestroy();
+    } else {
+      onHostDestroyImpl();
+    }
+  }
+
+  @ThreadConfined(UI)
+  private void onHostDestroyImpl() {
     UiThreadUtil.assertOnUiThread();
     mLifecycleState = LifecycleState.BEFORE_CREATE;
     for (LifecycleEventListener listener : mLifecycleEventListeners) {
@@ -370,19 +385,6 @@ public void onHostDestroy() {
         handleException(e);
       }
     }
-    resetCurrentActivity(false);
-  }
-
-  @ThreadConfined(UI)
-  public void onHostDestroy(boolean keepActivity) {
-    onHostDestroy();
-    resetCurrentActivity(keepActivity);
-  }
-
-  private void resetCurrentActivity(boolean keepActivity) {
-    if (!keepActivity) {
-      mCurrentActivity = null;
-    }
   }
 
   /** Destroy this instance, making it unusable. */