Loading for lazy-load strategy is not showing in react-router v7

Nobody has claimed this yet.

**What you were expecting:**
RA lazy strategy with loading should work properly after update to react-router v7.

**What happened instead:**

Loading component not initiate in Suspense when update my App to react-router v7.

**Steps to reproduce:**
1. Create router that import lazy components;
2. Navigate with slow network to understand the problem, setted in the Browser;
3. Loading componente will not be initiated by RA Suspense;

This strategy solved my problem:
https://github.com/remix-run/react-router/issues/12474

I think that we can put key inside the Suspense to solve the problem: https://github.com/marmelab/react-admin/blob/377f29f0c4357281838e978fa613acb29c6dbe2b/packages/ra-ui-materialui/src/layout/Layout.tsx#L70

like:

```tsx
function MyComp() {
const location = useLocation()

return (
}
key={location.key}
>


)
}

```

**Other information:**

**Environment**

* React-admin version: 5.8.4
* Last version that did not exhibit the issue (if applicable):
* React version: v18
* Browser: chrome
* Stack trace (in case of a JS error):

Start with packages/ra-ui-materialui/src/layout/Layout.tsx around the Suspense boundary linked in the issue, then reproduce the lazy-route navigation with a slow network after upgrading to react-router v7. Compare the behavior with the linked react-router strategy; done means the LoadingComp fallback is initiated while the lazy component loads.

Written by the indexing model from the issue text.