Hide some more unused things from the API

Author: dcharkes

pkgs/native_assets_cli/lib/src/api/build_output.dart

@@ -15,15 +15,6 @@ import 'dependencies.dart';
 import 'metadata.dart';
 
 abstract class BuildOutput {
-  /// Time the build this output belongs to started.
-  ///
-  /// Rounded down to whole seconds, because [File.lastModified] is rounded
-  /// to whole seconds and caching logic compares these timestamps.
-  DateTime get timestamp;
-  List<Asset> get assets;
-  Dependencies get dependencies;
-  Metadata get metadata;
-
   factory BuildOutput({
     DateTime? timestamp,
     List<Asset>? assets,