php: Support typed class constants

[nsfisis]

Part of #2169

Support typed class constants introduced since PHP 8.3.

https://wiki.php.net/rfc/typed_class_constants

class C {
    const bool CONST_1 = true;
    public const int CONST_2 = 1;
    protected const float CONST_3 = 1.0;
    private const string CONST_4 = "foo";
    const ?array CONST_5 = [];
}