feat(ui): remove isRefinerAvailable state, update refiner node

We can derive `isRefinerAvailable` from the query result (eg are there any refiner models installed). This is a piece of server state, so by using the list models response directly, we can avoid needing to manually keep the client in sync with the server.

Created a `useIsRefinerAvailable()` hook to return this boolean wherever it is needed.

Also updated the main models & refiner models endpoints to only return the appropriate models. Now we don't need to filter the data on these endpoints.

invokeai/frontend/web/src/features/parameters/components/Parameters/MainModel/ParamMainModelSelect.tsx

@@ -40,7 +40,7 @@ const ParamMainModelSelect = () => {
     const data: SelectItem[] = [];
 
     forEach(mainModels.entities, (model, id) => {
-      if (!model || ['sdxl-refiner'].includes(model.base_model)) {
+      if (!model) {
         return;
       }