Allow passing --changed cli option to vitest

### Command

test

### Description

The `unit-test` builder does not provide a way to use the `--changed` vitest option: https://vitest.dev/guide/cli.html#changed. This will analyze the import graph and only run tests affected by a change, which is useful for running a subset of the test suite for pull requests. This option is not available through the vitest configuration file.

### Describe the solution you'd like

Add a `changed: ` option to the `unit-test` builder options which passes `--changed ` to the vitest runner.

### Describe alternatives you've considered

I don't think there are any good workarounds. Using `@analogjs/vitest-angular` exposes vitest directly, but requires more setup and is not an "official" package.

Commencez par les options du builder de tests unitaires et suivez la manière dont elles sont transmises au runner Vitest. Vérifiez qu’une option string modifiée transmet --changed et que les tests pertinents du builder couvrent la commande obtenue.

Rédigé par le modèle d'indexation à partir du texte de l'issue.