Trap focus in the side panel for resource preview

[marcellamaki]

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Observed behavior

When a user previews a resource within the import from channels experience, the focus is not trapped in the side panel, and can get "lost" behind the drawer.

Expected behavior

Within a side panel, the focus should be trapped. (This issue is not to remediate all places in studio where this may exist, just this one 🙂)

Reported by Liana in the search recommendations bug hunt

[akolson]

Fixes by #5400