## Summary

The diagnostics panel was ignoring the user's `toolbar.breadcrumbs`
setting and always showing breadcrumbs. This makes both
`BufferDiagnosticsEditor` and `ProjectDiagnosticsEditor` check the
`EditorSettings` to determine whether to display breadcrumbs.

## Changes

- `buffer_diagnostics.rs`: Updated `breadcrumb_location` to check
`EditorSettings::get_global(cx).toolbar.breadcrumbs`
- `diagnostics.rs`: Updated `breadcrumb_location` to check
`EditorSettings::get_global(cx).toolbar.breadcrumbs`

This follows the same pattern used by the regular `Editor` in
`items.rs`.

## Test plan

1. Set `toolbar.breadcrumbs` to `false` in settings.json
2. Open a file with diagnostics
3. Run `diagnostics: deploy current file`
4. Verify that breadcrumbs are hidden in the diagnostics panel

Fixes #43020