Moved kegs from ARGV to args.rb

[zachauten]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew tests with your changes locally?

---

#5730

[zachauten]

Still a work in progress, meant to open as a draft.

[MikeMcQuaid]

@zachauten Cool, shout when you're done/need help! @GauthamGoli may have useful thoughts too.

[zachauten]

@MikeMcQuaid @GauthamGoli Ready for review!

[MikeMcQuaid]

Great work, thanks again @zachauten!