Closes https://github.com/zed-industries/zed/discussions/53471

Adds a requirement on status bar items to provide a way to hide
themselves.

<img width="329" height="153" alt="image"
src="https://github.com/user-attachments/assets/b98ee5ba-a439-44d7-9ab5-f4511b66a574"
/>

<img width="464" height="40" alt="image"
src="https://github.com/user-attachments/assets/b41d9189-3475-4e61-b3a4-bc731dd52c53"
/>


Release Notes:

- Added a way to hide sidebar buttons