Unify deployment_platform interface with CE

Make sure we override the method from CE, too

app/models/concerns/deployment_platform.rb

 module DeploymentPlatform
-  def deployment_platform
+  # EE would override this and utilize the extra argument
+  def deployment_platform(environment: nil)
     @deployment_platform ||=
       find_cluster_platform_kubernetes ||
       find_kubernetes_service_integration ||

app/models/environment.rb

@@ -229,7 +229,7 @@ class Environment < ActiveRecord::Base
   end
 
   def deployment_platform
-    project.deployment_platform
+    project.deployment_platform(environment: self)
   end
 
   private

ee/app/models/concerns/ee/deployment_platform.rb

 module EE
   module DeploymentPlatform
+    extend ::Gitlab::Utils::Override
+
+    override :deployment_platform
     def deployment_platform(environment: nil)
       return super unless environment && feature_available?(:multiple_clusters)