This PR upgrades the workspace's app state to a strong pointer. It's an
app-global concern, and it should only die when the app dies. When the
app dies the process exits, so the cyclic reference problem isn't an
issue.
Self-Review Checklist:
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable
Release Notes:
- N/A
Mikayla Maki
b1415bcdc6