This PR adds additional background and border colors for each of the
status colors to the theme.

These colors are then used to style the diagnostic popovers:

<img width="407" alt="Screenshot 2024-01-02 at 4 25 50 PM"
src="https://github.com/zed-industries/zed/assets/1486634/fbc64ea7-3dcd-43b7-8520-91f16304bfba">

<img width="396" alt="Screenshot 2024-01-02 at 4 26 05 PM"
src="https://github.com/zed-industries/zed/assets/1486634/6e4a44bf-4aac-4595-afff-7fbf8b2b9e1f">

Release Notes:

- N/A