feat(FormField): signal forms support

### Feature Description

The first (experimental) version of Signal Forms will land in Angular 21.
This is awesome news, because with Signal Forms, forms finally become fully reactive, functional and composable.
I would like to be able to use Signal Forms with Angular Material.

For an outsider, it is impossible to see whether Angular Material support for Signal Forms:
1. Will just work out-of-the-box
2. Will require some small changes in Angular Material
3. Requires a huge amount of work in Angular Material

### Use Case

As a developer, I love the improvements that Signal Forms will bring to our code base.
I am really looking forward to using them in tandem with Angular Material.

Beginne mit der Überprüfung von Angular 21 Signal Forms und der vorhandenen Angular Material form-field components. Ermittle, ob Signal Forms ohne Anpassungen funktionieren oder Änderungen erfordern, und dokumentiere anschließend die betroffenen Komponenten, Tests und das Kompatibilitätsergebnis.

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