This PR prevents the breadcrumbs from overflowing the toolbar when its
contents are long:

<img width="1270" alt="Screenshot 2024-01-19 at 6 15 58 PM"
src="https://github.com/zed-industries/zed/assets/1486634/ecee7a42-51ef-43d4-99a1-9c3da784dede">

Release Notes:

- Fixed an issue where long breadcrumbs would overflow the toolbar.