Add support for persistent storage of panel layouts, sizes, and active tabs (#4017)

* Add persistence to panel layouts

* Fix and persist the Window > Focus Document mode

* Add a Window > Reset Workspace action

* workspace_layout.json -> workspace_layout.ron

* Fix native app hole punch

* Cleanup review pass

frontend/src/stores/portfolio.ts

@@ -18,7 +18,7 @@ const initialState: PortfolioStoreState = {
 	unsaved: false,
 	documents: [],
 	activeDocumentIndex: 0,
-	panelLayout: { root: { Split: { children: [] } }, nextGroupId: 0n },
+	panelLayout: {},
 };
 
 let subscriptionsRouter: SubscriptionsRouter | undefined = undefined;