let's use Xnav instead of `XPathFactory`

[yegor256]

For better performance, it may be helpful to use Xnav instead of XPathFactory, in XPathDirective.

[yegor256]

@volodya-lombrozo please, help with this one, when you have time

[volodya-lombrozo]

@yegor256 Sure, could you assign it to me, please?