Add English documentation comments to all benchmark_cherrypick source files (adapters, scenarios, CLI, reporters, runner)

benchmark_cherrypick/lib/scenarios/universal_service.dart

@@ -1,10 +1,17 @@
 
+/// Base interface for any universal service in the benchmarks.
+///
+/// Represents an object in the dependency chain with an identifiable value
+/// and (optionally) a dependency on a previous service in the chain.
 abstract class UniversalService {
+  /// String ID for this service instance (e.g. chain/level info).
   final String value;
+  /// Optional reference to dependency service in the chain.
   final UniversalService? dependency;
   UniversalService({required this.value, this.dependency});
 }
 
+/// Default implementation for [UniversalService] used in service chains.
 class UniversalServiceImpl extends UniversalService {
   UniversalServiceImpl({required super.value, super.dependency});
 }