docs: Add Virtualizer docs (#7700)
* wip: Virtualizer docs
* Remove UNSTABLE prefix
* Update JS docs
* update content
* Revert useListBox docs for now
* Fix TS
* lint
* slight text update
* Update packages/react-aria-components/src/Virtualizer.tsx
Co-authored-by: Reid Barber <reid@reidbarber.com>
* review comments
* Remove UNSTABLE prefix from CollectionRendererContext
* Use gap in TreeView
* fix keyboard navigation of custom layout example
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Co-authored-by: Reid Barber <reid@reidbarber.com>
