Add generator for permission definition files

What does this MR do and why?

The groupauthorization team is working to standardize permissions in the product and as part of that work will implement permission definition files that will be used to automate documentation and eventually aid in other actions. This MR adds a rails generator for these permission definition files.

References

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Run the generator to create a permission definition file.

bundle exec rails generate authz:permission read_stuff

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #568175