Use qualified name for types

Qualified name specifies the name from the root namespace. This will prevent errors in the future where we have clashing constant names that were separated by their fully qualified names. During RBI generation we used to drop the leading `::` anchors and the constant would point to a wrong type than what the developer intended.

e.g. #466

lib/tapioca/sorbet_ext/name_patch.rb

@@ -6,7 +6,22 @@ module Types
     class Simple
       module NamePatch
         def name
-          @name ||= ::Tapioca::Reflection.name_of(@raw_type).freeze
+          @qualified_name ||= qualified_name_of(@raw_type).freeze
+        end
+
+        private
+
+        NAME_METHOD = Module.instance_method(:name)
+
+        def qualified_name_of(constant)
+          name = NAME_METHOD.bind(constant).call
+          return if name.nil?
+
+          if name.start_with?("::")
+            name
+          else
+            "::#{name}"
+          end
         end
       end