The flutter/engine additions to the frontend_server are entirely gone at this point: https://github.com/flutter/engine/blob/master/flutter_frontend_server/lib/server.dart

Now that the Dart SDK is building it, we could save some upload/download time and simplify the engine code base too.

• The Flutter CLI should stop using the flutter_frontend_server from the Engine build.
• Remove internal usage: b/233000852, b/305121780
• Reland Revert "Remove the frontend server wrapper" engine#46863 and Fix --no-prebuilt-dart-sdk build engine#46842
• The Engine recipes should stop packaging the flutter_frontend_server (https://flutter-review.googlesource.com/c/recipes/+/30240)
• The flutter_frontend_server should be removed from the Engine.