Allow tests to pass without any test files (e.g. via Vitest `passWithNoTests`)

### Command

test

### Description

Executing the **test** command on a project (app or lib) that does not have any test files (yet) will always lead to the following error message:

```txt
An exception occurred while getting runner-specific build options:
Error: No tests found matching the following patterns:
- Included: **/*.spec.ts, **/*.test.ts

Please check the 'test' target configuration in your project's 'angular.json' file.
```

However, many use cases exist where this behaviour is unintended. For example, a freshly generated project (even more so in a monorepo) will often start out without any real test cases defined, and it even may take some time for the first ones to be written. Even at this early point, though, I (as a developer) will usually want to already integrate test execution into a quality gate setup (like continuous integration).

Currently, the Angular CLI does not offer a way to allow the **test** command to succeed when no test files exist.

Related issue: https://github.com/nrwl/nx/issues/34241

### Describe the solution you'd like

The most pragmatic solution would probably be:

- Remove the custom Angular CLI check for test files, see: https://github.com/angular/angular-cli/blob/5adc92541433be23fc2246db5a199cf5c0dc9e67/packages/angular/build/src/builders/unit-test/runners/vitest/build-options.ts#L161-L170
- Instead, rely on Vitest and its `passWithNoTests` option - which is `false` by default, so no breaking change is to be expected (besides a different log message)

### Describe alternatives you've considered

Alternatively:

- The Angular CLI **test** command could also expose its own option. This would however collide with the respective Vitest option and thus require conflict resolution / priority checks. Plus, skimming the source code leads me to believe that the Angular CLI is currently not actively loading any custom Vite config, just passing it on - so changes here would presumably affect multiple places.

Beginne mit packages/angular/build/src/builders/unit-test/runners/vitest/build-options.ts bei den Zeilen 161-170, wo die benutzerdefinierte Prüfung auf keine Testdateien beschrieben wird. Überprüfe, wie der Testbefehl Runner-Optionen an Vitest übergibt, und verifiziere anschließend, dass ein Projekt ohne Testdateien mit Vitest's passWithNoTests-Option erfolgreich ist, während das Standardverhalten unverändert bleibt.

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