Script Generator: Sort out python locations

As a user, I would like to be able to use the script generator without being dependent upon genie python/our python distribution.

This ticket is to have a discussion about where to store the python used in a script generator. It is a result of the script generator code chat where we discussed the idea that we don't necessarily need ActionDefinition and cast_parameters_to in genie python.

Acceptance criteria:
- [ ] Discussion
- [ ] Decision noted
- [ ] Ticket created to do it