This PR restores the controlled nature of focus. Focus allows keyboard
shortcuts and other interactions to occur. The editor's focus should
always / entirely be controlled via the autoFocus prop or by manually
setting `editor.instanceState.isFocused`.
Design note: I'm starting to think that focus is the wrong abstraction,
and that we should instead use a kind of "disabled" state for editors
that the user isn't interacting with directly. In a page where multiple
editors exit (e.g. a notion page), a developer could switch from
disabled to enabled using a first interaction.
### Change Type
- [x] `patch` — Bug fix
### Test Plan
- [x] End to end tests
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