inline collections_controller_resource_spec to existing tests

`dashboard/collections_controller_resource_spec` is a slightly divergent
copy-paste of the same tests in `dashboard/collections_controller_spec`. this
creates a major maintenance burden, and some weird misdirection when navigating
the codebase (how will i know to look for tests on the Controller here?).

the more immediate problem is that this whole test setup is flaky and the whole
file can fail en masse.

as a first step(?) for a fix, we want to inline all the tests so they run
identically and setup for both sets of specs is in one place. this is a straight
inline, removing the duplicate tests. some attention was given to resolving
drift between the specs.

app/models/hyrax/collection_type.rb

@@ -49,7 +49,10 @@ def title=(value)
     # @return [Hyrax::PcdmCollection | ::Collection] an instance of Hyrax::CollectionType with id = the model_id portion of the gid (e.g. 3)
     # @raise [ActiveRecord::RecordNotFound] if record matching gid is not found
     def self.for(collection:)
-      find_by_gid!(collection.collection_type_gid)
+      gid = collection.collection_type_gid
+      gid = gid.first if gid.is_a?(Enumerable)
+
+      find_by_gid!(gid)
     end
 
     # Find the collection type associated with the Global Identifier (gid)

spec/controllers/hyrax/collections_controller_spec.rb

@@ -135,4 +135,6 @@
       end
     end
   end
+
+  context "using a Valkyrie CollectionResource model"
 end