Refactor: In JavaTurboModule, use jobject to hold module object

Summary:
## Rationale
JavaTurboModule holds the module object as a JTurboModule. With the TurboModule inteorp layer, JavaTurboModule will also need to hold NativeModule objects.

## Changes
So, this diff makes JavaTurboModule hold the module object as a jobject instead.

This shouldn't impact method dispatch, because method dispatch doesn't rely on the JTurboModule interface.

Changelog: [Internal]

Reviewed By: mdvacca

Differential Revision: D43918939

fbshipit-source-id: 7cc43dfe2df7571e39bcf4d6f362dde0e500e2fe

ReactCommon/react/nativemodule/core/platform/android/ReactCommon/JavaTurboModule.h

@@ -30,7 +30,7 @@ class JSI_EXPORT JavaTurboModule : public TurboModule {
   // TODO(T65603471): Should we unify this with a Fabric abstraction?
   struct InitParams {
     std::string moduleName;
-    jni::alias_ref<JTurboModule> instance;
+    jni::alias_ref<jobject> instance;
     std::shared_ptr<CallInvoker> jsInvoker;
     std::shared_ptr<CallInvoker> nativeInvoker;
   };
@@ -48,7 +48,8 @@ class JSI_EXPORT JavaTurboModule : public TurboModule {
       jmethodID &cachedMethodID);
 
  private:
-  jni::global_ref<JTurboModule> instance_;
+  // instance_ can be of type JTurboModule, or JNativeModule
+  jni::global_ref<jobject> instance_;
   std::shared_ptr<CallInvoker> nativeInvoker_;
 };