Route-specific app-shell: prerendering dynamic parameterized pages

### Which @angular/* package(s) are relevant/related to the feature request?

platform-server

### Description

We have a use case, where we would like to always show the same prerendered page skeleton/carcass on a route that has dynamic parameters.
Looking at the new Angular server documentation, I do not see such option https://angular.dev/guide/hybrid-rendering#parameterized-routes.

Basically we would like `posts/:id` to return a single prerendered page for any `:id` parameter.

This page would show a loading skeleton and would let the browser handle the exact `:id` and the logic related to it.

### Proposed solution

Add a wildcard `**` route option that would indicate to Angular that this prerendered page handles any dynamic route parameters.

These wildcards could be used as the dynamic parameter in the build time when prerendering happens. It would be the component's responsibility to correctly handle the `**` parameter and show some parameter-agnostic content (loaders/skeletons) that would then be prerendered by Angular and served by the server accordingly.

How it could look in `app.routes.server.ts`:
```
{
path: 'posts/**',
renderMode: RenderMode.Prerender
},
```

Excerpt from the imaginary `post.component.ts`:
```
private subscribeRouter() { // called in ngOnInit
this.activatedRoute.params
.pipe(takeUntilDestroyed(this.destroyRef))
.subscribe(params => {
const id: string = params.id;

if (id === '**') {
this.isCarcass = true; // post.component.html will render some skeleton/loader if isCarcass === true
} else {
this.getPost(id);
}
});
}
```

### Alternatives considered

I am currently considering:
1. Adding a "fake" route parameter that I would configure Angular to prerender.
2. This route would render the skeleton/carcass of the page as per my use case.
3. Serving the route myself in `server.ts` with a middleware that runs before any middleware generated by Angular CLI.

`app.routes.server.ts`:
```
{
path: 'posts/:id',
renderMode: RenderMode.Prerender,
getPrerenderParams(): Promise[]> {
return Promise.resolve(['carcass'].map(i => ({ id: i })));
}, // prerenders in browser/posts/carcass
},
```

`server.ts`:
```
// My new middleware
app.use(
'/posts/:id',
express.static(join(browserDistFolder, 'posts', 'carcass', 'index.html'), {
maxAge: '1y',
redirect: false,
}),
);

// Default generated by Angular
app.use(
express.static(browserDistFolder, {
maxAge: '1y',
index: false,
redirect: false,
}),
);

// Default generated by Angular
app.get('/**', (req, res, next) => {
angularApp
.handle(req)
.then(response =>
response ? writeResponseToNodeResponse(response, res) : next(),
)
.catch(next);
});
```

I have tested this approach and it works fine, however, it feels pretty hacky.

Start with Angular's hybrid-rendering documentation for parameterized routes, then inspect the prerender route configuration shown in app.routes.server.ts and the server middleware example in server.ts. Compare the requested posts/** behavior with the existing getPrerenderParams approach; done means a route-specific prerendered skeleton can serve arbitrary dynamic parameters without custom middleware.

Written by the indexing model from the issue text.