Show error and warning indicators in tabs

[nilskch]

Check for existing issues

• Completed

Describe the feature

In #18182, we introduced diagnostics to the project panel using a DecoratedIcon with X or triangle decorations for errors and warnings. It would be great to also show diagnostics in the tab bar as well, using the same approach. I would also use the same setting we used in the "project_panel".

{
  "tabs": {
    // "all" / "errors" / "off"
    "show_diagnostics": "all"
  }
}

I am happy to implement this feature if you would want to add this to Zed.

Environment

Zed: v0.163.2 (Zed Preview)
OS: macOS 15.1.1
Memory: 18 GiB
Architecture: aarch64

If applicable, add mockups / screenshots to help present your vision of the feature

[nilskch]

@danilo-leal @iamnbutler what do you think about this? This would be relatively easy to implement since we can copy the design from the project panel.

[nilskch]

related to #4901 (comment)