Abstract Builder class to share some parameters

[Nayuta403]

Use case

Create from:
flutter/engine#36963 (comment)

Now we have too many builders, NewEngineIntentBuilder, CachedEngineIntentBuilder, as well as the increase of NewEngineInGroupIntentBuilder. They have some common parameters (especially NewEngineIntentBuilder and NewEngineInGroupIntentBuilder, because they are starting a new engine), in FlutterActivity, FlutterFragmentActivity, FlutterFragment all appear.

Proposal

Abstract a Builder class with some parameters used by Dart like entryPoint, initialRoute, dartEntrypointArgs. Then Actvitity or fragments of the Builder extends from this class, and contains specific attributes, such as activityClass/fragmentClass. Many of such NewEngineIntentBuilder and NewEngineInGroupIntentBuilder fields can be Shared.