[5574] - add moveBefore and moveAfter to useTreeData

[rob-clayburn]

Closes #5574

Add moveBefore (which looks to me like it is actually just an alias for move) and moveAfter methods to the useTreeData hook.

This is my first time submitting a PR to the project, so please let me know if I've got something wrong in the process!

✅ 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).
• [ n/a] Looked at the Accessibility Practices for this feature - Aria Practices

📝 Test Instructions:

I believe this is just internal atm - so running the new unit tests should be sufficient.

[reidbarber]

Thanks for the PR! You'll need to sign the CLA to get the build to pass.

[rob-clayburn]

thanks - had to wait to get approval from my company. All good now and I've signed the agreement

[snowystinger]

lgtm, and thanks for the tests!

[reidbarber]

Thanks!