Collect push_configs in the Plugin Manager

lib/vagrant/plugin/v2/manager.rb

@@ -183,6 +183,17 @@ module Vagrant
           end
         end
 
+        # This returns all the config classes for the various pushes.
+        #
+        # @return [Registry]
+        def push_configs
+          Registry.new.tap do |result|
+            @registered.each do |plugin|
+              result.merge!(plugin.components.configs[:push])
+            end
+          end
+        end
+
         # This returns all synced folder implementations.
         #
         # @return [Registry]