Use polymorphic_paths where we can

To reduce the number of abstract methods, use polymorphic_paths for
collection routes. Unfortunately for member routes, polymorphic_paths
does not support namespaced classes, so still continue to override
methods.

app/presenters/clusterable_presenter.rb

@@ -17,23 +17,19 @@ class ClusterablePresenter < Gitlab::View::Presenter::Delegated
   end
 
   def index_path
-    raise NotImplementedError
+    polymorphic_path([clusterable, :clusters])
   end
 
   def new_path
-    raise NotImplementedError
-  end
-
-  def clusterable_params
-    raise NotImplementedError
+    new_polymorphic_path([clusterable, :cluster])
   end
 
   def create_user_clusters_path
-    raise NotImplementedError
+    polymorphic_path([clusterable, :clusters], action: :create_user)
   end
 
   def create_gcp_clusters_path
-    raise NotImplementedError
+    polymorphic_path([clusterable, :clusters], action: :create_gcp)
   end
 
   def cluster_status_cluster_path(cluster, params = {})

app/presenters/project_clusterable_presenter.rb

 # frozen_string_literal: true
 
 class ProjectClusterablePresenter < ClusterablePresenter
-  def index_path
-    project_clusters_path(clusterable)
-  end
-
-  def new_path
-    new_project_cluster_path(clusterable)
-  end
-
-  def create_user_clusters_path
-    create_user_project_clusters_path(clusterable)
-  end
-
-  def create_gcp_clusters_path
-    create_gcp_project_clusters_path(clusterable)
-  end
-
   def cluster_status_cluster_path(cluster, params = {})
     cluster_status_project_cluster_path(clusterable, cluster, params)
   end
@@ -28,8 +12,4 @@ class ProjectClusterablePresenter < ClusterablePresenter
   def cluster_path(cluster, params = {})
     project_cluster_path(clusterable, cluster, params)
   end
-
-  def clusterable_params
-    { project_id: clusterable.to_param, namespace_id: clusterable.namespace.to_param }
-  end
 end