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favicon.ico is outdated and obsolete relic from the 90s.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

先追蹤建立 favicon 的 schematic 檔案以及 angular.json 中的相關項目，接著檢查 src/assets 中目前的圖示。確認產生的應用程式應包含哪些現代 PNG 或以 manifest 為基礎的檔案，移除過時的 favicon.ico 參照，並在相關的 schematic 測試涵蓋產生的 asset 時更新這些測試。

由索引模型根據 Issue 內容生成。