editor: Add toggle diagnostics to command palette (#31358)

Follow-up to #30316

This PR adds the `editor: toggle diagnostics` action to the comand
palette so that it can also be invoked that way.

I also ensures this, the `toggle inline diagnostics` and `toggle
minimap` actions are only registered if these are supported by the
current editor instance.

Release Notes:

- N/A

crates/editor/src/editor.rs

@@ -15446,8 +15446,7 @@ impl Editor {
             .max_severity
             .unwrap_or(self.diagnostics_max_severity);
 
-        if self.mode.is_minimap()
-            || !self.inline_diagnostics_enabled()
+        if !self.inline_diagnostics_enabled()
             || !self.show_inline_diagnostics
             || max_severity == DiagnosticSeverity::Off
         {