Return T from `IDependencyResolver.GetService<T>() (#5087)

Close #5086

Author: Aaronontheweb

src/contrib/dependencyinjection/Akka.DependencyInjection/IDependencyResolver.cs

@@ -20,7 +20,7 @@ namespace Akka.DependencyInjection
     public interface IDependencyResolver
     {
         IResolverScope CreateScope();
-        object GetService<T>();
+        T GetService<T>();
         object GetService(Type type);
 
         /// <summary>

src/contrib/dependencyinjection/Akka.DependencyInjection/ServiceProviderDependencyResolver.cs

@@ -30,7 +30,7 @@ public IResolverScope CreateScope()
             return new ServiceProviderScope(ServiceProvider.CreateScope());
         }
 
-        public object GetService<T>()
+        public T GetService<T>()
         {
             return ServiceProvider.GetService<T>();
         }