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" },
]
```

Start by tracing the Angular CLI code that resolves and copies the assets glob, using the configuration example in this issue as the expected input. Find the related asset-processing tests, then verify that a single matched asset can receive the configured filename while existing glob behavior remains unchanged.

Written by the indexing model from the issue text.