Add @DoNotStrip to stop obfuscation of Fabric related classes

Summary:
Proguard seems to keep Fabric methods a bit differently from Redex, with method signature lookup with `MountItem` and `StateWrapperImpl` failing in release RNTester builds because of mangled names. Adding these annotations should keep the classes, ensuring lookup from native is correct.

Changelog: [Internal] - Add DoNotStrip annotations to Fabric related classes

Reviewed By: ryancat

Differential Revision: D34726510

fbshipit-source-id: 0c1d8e1fabec75511942943b533ddd8b637a5e19

ReactAndroid/src/main/java/com/facebook/react/fabric/StateWrapperImpl.java

@@ -24,6 +24,7 @@ import com.facebook.react.uimanager.StateWrapper;
  * the Bindings.cpp, where the pointer to the C++ event emitter is set.
  */
 @SuppressLint("MissingNativeLoadLibrary")
+@DoNotStrip
 public class StateWrapperImpl implements StateWrapper {
   static {
     FabricSoLoader.staticInit();

ReactAndroid/src/main/java/com/facebook/react/fabric/mounting/mountitems/MountItem.java

@@ -10,8 +10,10 @@ package com.facebook.react.fabric.mounting.mountitems;
 import androidx.annotation.AnyThread;
 import androidx.annotation.NonNull;
 import androidx.annotation.UiThread;
+import com.facebook.proguard.annotations.DoNotStrip;
 import com.facebook.react.fabric.mounting.MountingManager;
 
+@DoNotStrip
 public interface MountItem {
 
   /** Execute this {@link MountItem} into the operation queue received by parameter. */