Introduce manage_cluster queue for sidekiq workers

app/workers/cluster_creation_worker.rb

 class ClusterCreationWorker
   include Sidekiq::Worker
-  include DedicatedSidekiqQueue
+  include ClusterQueue
   def perform(cluster_id)
     Gcp::Cluster.find_by_id(cluster_id).try do |cluster|

app/workers/concerns/cluster_queue.rb

+##
+# Concern for setting Sidekiq settings for the various Gcp clusters workers.
+#
+module ClusterQueue
+  extend ActiveSupport::Concern
+
+  included do
+    sidekiq_options queue: :manage_cluster
+  end
+end

app/workers/wait_for_cluster_creation_worker.rb

 class WaitForClusterCreationWorker
   include Sidekiq::Worker
-  include DedicatedSidekiqQueue
+  include ClusterQueue
   INITIAL_INTERVAL = 2.minutes
   EAGER_INTERVAL = 10.seconds

config/sidekiq_queues.yml

@@ -62,5 +62,4 @@
   - [update_user_activity, 1]
   - [propagate_service_template, 1]
   - [background_migration, 1]
-  - [cluster_creation, 1]
-  - [wait_for_cluster_creation, 1]
+  - [manage_cluster, 1]