test: add regression tests for scalar value casting with asRoot

[devnix]

Route and query parameters from an HTTP request are always strings, and the mapper enables scalar value casting for them, as documented:

Route and query parameter values coming from an HTTP request are typically strings. The mapper automatically handles scalar value casting for these parameters: a string "42" will be properly mapped to an int parameter.

The existing asRoot test cases pass native values ('anotherQueryParameter' => 42); that path is never exercised with the strings a real framework provides. This adds two cases: one mapping all query parameters to a shaped array, one to an object alongside a #[FromRoute] parameter.

This is not a bug report: master already behaves correctly. The bug existed on 2.5.1 and was fixed incidentally by 578bd58 (chore: refactor HTTP request mapping), a commit not yet in any release. These tests pin the fix down.

Reproduction on 2.5.1:

$request = new HttpRequest(queryParameters: ['page' => '42']);

// Works.
(new MapperBuilder())->argumentsMapper()->mapArguments(
    fn (#[FromQuery] int $page) => [],
    $request,
); // => ['page' => 42]

// Fails.
(new MapperBuilder())->argumentsMapper()->mapArguments(
    /** @param array{page: int} $query */
    fn (#[FromQuery(asRoot: true)] array $query) => [],
    $request,
); // => MappingError: An error occurred at path page: Value '42' is not a valid integer.

These tests guard the fix. Reverting the change in HttpRequestNodeBuilder (excluding the asRoot key from allowScalarValueCastingForChildren()) makes both fail with Value '42' is not a valid integer; the other 56 cases in the file pass.

Happy to adjust naming or placement if you prefer them elsewhere.

[romm]

Thank you!