This allows applications to start a Flutter engine instance during app startup
and keep it running throughout the app process' lifetime.
FlutterActivity subclasses can override createFlutterNativeView to provide a
preinitialized FlutterNativeView instance and override retainFlutterNativeView
to signal that the FlutterNativeView should be kept alive when the activity
is destroyed.
* This adds rpc call to simply set asset path.
This is needed when doing hot reload to pick up updated assets.
* Move asset_directory fetch for after view_id. Clean up return. Fix formatting.
* Add SetAssetBundlePath methods implementations for mac and ios
* Fix mac mm
* Fix formatting
* Merge and use nullptr
