refactor(core): separate editor & doc mode (#7873)

doc.mode -> primaryMode
(*new) editor.mode

New Service:
editor service

Change Mode:

```
const editor = useService(EditorService).editor;
editor.setMode('page')
```

Change primary mode

```
const editor = useService(EditorService).editor;
editor.doc.setPrimaryMode('page')
```

packages/frontend/core/src/bootstrap/first-app-data.ts

@@ -31,7 +31,7 @@ export async function buildShowcaseWorkspace(
   );
 
   if (defaultDoc) {
-    defaultDoc.setMode('edgeless');
+    defaultDoc.setPrimaryMode('edgeless');
   }
 
   dispose();