feat: add getState for StateWrapperImpl (#48255)

Summary:
We're trying to pass `jsi::Value`s directly to our view components (and convert them to java/swift types manually). That way we can pass "complex" objects to our views (such as `jsi::Object`s with `NativeState` attached, without the need to convert them to e.g. `folly::dynamic`).

On android we store our complex prop values on the `StateWrapperImpl` to pass the complex types between c++ and java/kotlin. See an example here:

https://github.com/hannojg/nitro/blob/2378fe7754294c496b2cbcd62f7109529e276427/packages/react-native-nitro-image/nitrogen/generated/android/c%2B%2B/JValueFromStateWrapper.cpp#L21-L23

```
  const auto& customStateData = dynamic_cast<const ConcreteState<CustomStateData>&>(state);
  CustomStateData data = customStateData.getData();
  std::shared_ptr<HybridTestObjectSwiftKotlinSpec> nativeProp = data.nativeProp;
```

> (And then it might be used in java like this:)
https://github.com/hannojg/nitro/blob/2378fe7754294c496b2cbcd62f7109529e276427/packages/react-native-nitro-image/android/src/main/java/com/margelo/nitro/image/NitroExampleViewManager.java#L31-L38

```kotlin
public Object updateState(NonNull View view, ReactStylesDiffMap props, StateWrapper stateWrapper) {
   StateWrapperImpl stateWrapperImpl = (StateWrapperImpl) stateWrapper;

    HybridTestObjectSwiftKotlinSpec nativeProp = ValueFromStateWrapper.valueFromStateWrapper(stateWrapperImpl);
    long value = nativeProp.getBigintValue();
    Log.d("NitroExampleViewManager", "Value from state: " + value);
```

For that we need to be able to access the underlying state, which is what we added in this PR.

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[ANDROID] [ADDED] - Added `getState` method for `StateWrapperImpl`

Pull Request resolved: https://github.com/facebook/react-native/pull/48255

Test Plan: Internal change, just make sure all tests are passing

Reviewed By: cipolleschi

Differential Revision: D67196130

Pulled By: javache

fbshipit-source-id: 7da74bcddef79abd3122baaad1bfce30330ecc80

packages/react-native/ReactAndroid/src/main/jni/react/fabric/StateWrapperImpl.cpp

@@ -56,6 +56,10 @@ void StateWrapperImpl::setState(std::shared_ptr<const State> state) {
   state_ = state;
 }
 
+std::shared_ptr<const State> StateWrapperImpl::getState() const {
+  return state_;
+}
+
 void StateWrapperImpl::registerNatives() {
   registerHybrid({
       makeNativeMethod("initHybrid", StateWrapperImpl::initHybrid),

packages/react-native/ReactAndroid/src/main/jni/react/fabric/StateWrapperImpl.h

@@ -29,6 +29,7 @@ class StateWrapperImpl : public jni::HybridClass<StateWrapperImpl> {
   jni::local_ref<ReadableNativeMap::jhybridobject> getStateDataImpl();
   void updateStateImpl(NativeMap* map);
   void setState(std::shared_ptr<const State> state);
+  std::shared_ptr<const State> getState() const;
 
  private:
   std::shared_ptr<const State> state_;