Introduce ReactPackageTurboModuleManagerDelegate

Summary:
## Summary
People use `ReactPackage` instances to create NativeModules. To make the migration from NativeModule to TurboModule easy, I'm introducing a `TurboModuleManagerDelegate` that understands `ReactPackage`s, and uses them to lookup and create the Java TurboModule objects. This way, we don't have to change the way we declare NativeModules for the migration.

## TurboModule registration
Each application should have its own subclass of `ReactPackageTurboModuleManagerDelegate`. This subclass is a hybrid class with a C++ and a Java part. The Java part can (and probably should) do nothing (for now). The C++ part has to implement the `moduleName -> jni::HostObject` and `moduleName, javaInstance -> jni::HostObject` functions for all TurboModules in the application.

**Use Case: Migrating a NativeModule to TurboModule system**
1. Make the Java NativeModule extend `TurboModule`. (The reason why this doesn't happen automatically is probably because we haven't changed the Java codegen yet).
2. Modify the `moduleName -> jni::HostObject` or `moduleName, javaInstance -> jni::HostObject` functions to return the `TurboModule`.

**Use Case: Adding a new TurboModule**
1. Add the TurboModule to a `ReactPackage` in the application.
2. Modify the `moduleName -> jni::HostObject` or `moduleName, javaInstance -> jni::HostObject` functions to return the TurboModule `jsi::HostObject`.

**Note:** It's also possible to declare TurboModules by overriding the `getModule(String moduleName)` function of `ReactPackageTurboModuleManagerDelegate`. It's not a good idea, because it'll make switching between the NativeModule/TurboModule system difficult.

Reviewed By: mdvacca

Differential Revision: D15209129

fbshipit-source-id: 4b0a303595145be9b19d6f4934f956b91990f859

ReactAndroid/src/main/java/com/facebook/react/LazyReactPackage.java

@@ -76,8 +76,7 @@ public abstract class LazyReactPackage implements ReactPackage {
    * @param reactContext
    * @return
    */
-  /* package */
-  Iterable<ModuleHolder> getNativeModuleIterator(final ReactApplicationContext reactContext) {
+  public Iterable<ModuleHolder> getNativeModuleIterator(final ReactApplicationContext reactContext) {
     final Map<String, ReactModuleInfo> reactModuleInfoMap =
         getReactModuleInfoProvider().getReactModuleInfos();
     final List<ModuleSpec> nativeModules = getNativeModules(reactContext);