Unfortunately I don't have a solution for you right now. I assume you want to define the support macros in a separate file, available for import. There is a Support files capability for question authors to provide extra files but these are intended for use in the sandbox (Jobe) environment, not for use on the Moodle server where Twig runs.
I'll put this in a "to think about" queue. I'm getting very worried about feature bloat - CodeRunner is already rather too complicated for many users.