Use ensure_compiled! instead of ensure_loaded? on map typespec macro

Instead of raising, holds the file compilation until the module is
available.

Solves compilation issue when using `one_file_per_module=true` and map types,
where it would raise due to `Code.ensure_loaded?` returning false for a
module that wasn't compiled yet.

Co-authored-by: Yordis Prieto <[email protected]>

Author: v0idpwn

lib/protobuf/dsl/typespecs.ex

@@ -58,10 +58,7 @@ defmodule Protobuf.DSL.Typespecs do
   end
 
   defp field_prop_to_spec(_syntax, %FieldProps{map?: true, type: map_mod} = prop) do
-    if not Code.ensure_loaded?(map_mod) do
-      raise "module #{inspect(map_mod)} was not loaded, but was expected to be since it's used as a map entry"
-    end
-
+    Code.ensure_compiled!(map_mod)
     map_props = map_mod.__message_props__()
 
     key_spec = scalar_type_to_spec(map_props.field_props[map_props.field_tags.key].type)