Restore "fix: Don’t focus first 'Item' of 'DropdownMenu' and 'SelectMenu' on open"

[smockle]

Reverts #1291, restoring #1270

When these lines (from #1270) removed temporary tabIndex from the container, certain browsers (e.g. Chrome) (but not others, e.g. Safari) set body as the activeElement. Because body is outside FocusTrap (and FocusZone), keyboard navigation between the container’s children was no longer possible.

By deferring the removal of the temporary tabIndex until the container has already lost focus, we avoid focusing body, and so we avoid breaking keyboard navigation. I added code comments in this PR to explain this slightly-more-complicated codepath and the scenario it prevents.

ℹ️ Reviewing this commit may help clarify the difference between this PR’s approach and that in #1270: b343d47

Screen recordings

Safari

Chrome

Checklist

• Tested in Safari
• Tested in Chrome

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🦋 Changeset detected

Latest commit: 763bb58

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

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@primer/components	Patch

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[dgreif]

Thanks for tracking this down 🏅