Replace favicon.ico in favor of png in src/assets

### Bug Report or Feature Request (mark with an `x`)
```
- [ ] bug report -> please search issues before submitting
- [x] feature request
```

### Area
```
- [ ] devkit
- [x] schematics
```

### Desired functionality
favicon.ico is outdated and obsolete relic from the 90s. Browsers for the past 2decades have supported png favicons. Additionally, while it's fairly easy now to generate a favicon.ico, it's just not needed or used anymore.

There's no reason imo to include favicon.ico, even for "compatibility". Removing the favicon.ico will also remove the entries needed in angular.json and remove the only asset stored outside of src/assets.

It should be replaced in favor of modern favicon methods. PWAs should use manifest.json

```



```
Note: svg doesn't have full browser support.

We haven't needed favicon.ico in years, but it's still widely used and implemented, even though all browsers support modern methods.

Commencez par retracer les fichiers de schematic qui créent le favicon ainsi que les entrées associées dans angular.json, puis examinez src/assets pour trouver l’icône actuelle. Confirmez quels fichiers modernes au format PNG ou basés sur un manifeste l’application générée devrait inclure, supprimez les références obsolètes à favicon.ico et mettez à jour les tests de schematic concernés s’ils couvrent les assets générés.

Rédigé par le modèle d'indexation à partir du texte de l'issue.