Properties with default values still get marked as required

[janikfu]

Since v4.15.0, we've encountered a problem regarding non-required properties
A property gets initialized in the constructor with a default value:

    public function __construct(
        #[Groups('docs')]
        #[Valid]
        private readonly CompanyQueryFilters $filters = new CompanyQueryFilters()
    ) {
    }

final readonly class CompanyQueryFilters {
    public function __construct(
        #[Groups('docs')]
        private ?string $organisation = null
    ) {
    }

    public function getOrganisation(): ?string {
        return $this->organisation;
    }
}

The schema output is as follows:

    "GetAllCompaniesQuery": {
        "required": [
            "filters"
        ],
        "properties": {
            "filters": {
                "$ref": "#/components/schemas/CompanyQueryFilters"
            }
        },
        "type": "object"
    },

We expect the filters-property to be non-required.

Follow-up on #2185 and #2179