Fix Nullsafe FIXMEs for CxxInspectorPackagerConnection.java and mark nullsafe (#50062)

Summary:
Pull Request resolved: #50062

Gone trough all the FIXMEs added in the previous diff by the nullsafe tool, marked the class as nullsafe and ensured no remaining violations.

Changelog: [Android][Fixed] Made CxxInspectorPackagerConnection.java nullsafe

Reviewed By: mdvacca

Differential Revision: D71126386

fbshipit-source-id: 94b6fca6972e5f08c22df7bebe6f853b5ceb20a7

Author: GijsWeterings

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

@@ -10,6 +10,7 @@
 import android.os.Handler;
 import android.os.Looper;
 import androidx.annotation.Nullable;
+import com.facebook.infer.annotation.Nullsafe;
 import com.facebook.jni.HybridData;
 import com.facebook.proguard.annotations.DoNotStrip;
 import java.io.Closeable;
@@ -21,7 +22,8 @@
 import okhttp3.WebSocketListener;
 
 /** Java wrapper around a C++ InspectorPackagerConnection. */
-/* package */ class CxxInspectorPackagerConnection implements IInspectorPackagerConnection {
+/* package */ @Nullsafe(Nullsafe.Mode.LOCAL)
+class CxxInspectorPackagerConnection implements IInspectorPackagerConnection {
   static {
     DevSupportSoLoader.staticInit();
   }
@@ -39,8 +41,7 @@ private static native HybridData initHybrid(
 
   public native void closeQuietly();
 
-  // NULLSAFE_FIXME[Inconsistent Subclass Parameter Annotation]
-  public native void sendEventToAllConnections(String event);
+  public native void sendEventToAllConnections(@Nullable String event);
 
   /** Java wrapper around a C++ IWebSocketDelegate, allowing us to call the interface from Java. */
   @DoNotStrip