feat: add SelectionGroup collection for Menu

[intergalacticspacehighway]

Closes

✅ Pull Request Checklist:

• [ ] Included link to corresponding React Spectrum GitHub Issue.
• [ ] Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• [ ] Filled out test instructions.
• [ ] Updated documentation (if it already exists for this component).
• [ ] Looked at the Accessibility Practices for this feature - Aria Practices

📝 Test Instructions:

🧢 Your Project:

[snowystinger]

Just to be clear, i know you just submitted this so that we'd have your prior work to go off of, these are mostly discussion points and figured this would be an ok place to start those discussions

[snowystinger]

Closing because we'll probably handle this differently in RAC and we can still refer back here for that work