node: split resolve_resources method

Split a separate method in the trait that is used to load resources, this allow to clean up the set_atts signature in most of the cases. Later we can think of moving the actual load of the resources to its own tree trasversal instead of doing it during parsing.

This is what I had in mind as a preliminary step in order to avoid a bit of code churn... too late for that :) but it might still be a good cleanup and prepare things for doing the resolution in its own step