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favicon.ico is outdated and obsolete relic from the 90s.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.

Inizia tracciando i file schematic che creano il favicon e le relative voci in angular.json, quindi esamina src/assets per individuare l’icona attuale. Conferma quali file moderni PNG o basati su manifest l’applicazione generata dovrebbe includere, rimuovi i riferimenti obsoleti a favicon.ico e aggiorna i test schematic pertinenti se coprono gli asset generati.

Scritto dal modello di indicizzazione a partire dal testo della issue.