Support renaming of asset file

### Feature request

It would be nice have an option to rename an asset in certain situations, e.g. when having conflicts in third party stuff.
Add property "filename" with the new file name.
Will only be used when the glob resolves to exactly one file.
```
"assets": [
{ "glob": "**/*", "input": "./assets/", "output": "./assets/" },
{ "glob": "favicon.ico", "input": "./", "output": "./", "filename": "newname.ico" },
]
```

先追蹤解析並複製 assets glob 的 Angular CLI 程式碼，使用此 issue 中的設定範例作為預期輸入。找出相關的 asset 處理測試，然後確認單一符合的 asset 可以使用設定的檔案名稱，同時維持現有的 glob 行為不變。

由索引模型根據 Issue 內容生成。