Fix DOMDocument::create*() return types

[staabm]

closes phpstan/phpstan#12278

see https://www.php.net/manual/en/class.domdocument.php

[ondrejmirtes]

I'd rather do benevolent unions here, because the failures are going to be rare.

[ondrejmirtes]

Thank you.

[dimadeush]

@ondrejmirtes Sometimes I can see that doc from PHPStorm is not the same as documentation on the php web site. F.e.

/**
     * Adds new child at the end of the children
     * @link https://php.net/manual/en/domnode.appendchild.php
     * @param DOMNode $node <p>
     * The appended child.
     * </p>
     * @return DOMNode The node added.
     */
    public function appendChild(DOMNode $node) {}

But on the php web-site we can see next:

public DOMNode::appendChild(DOMNode $node): DOMNode|false

Currently I don't know where the "proper" way and maybe we need to communicate JetBrains as of PHPStorm jar plugin related. Will be done with link to this example. Also I don't know if other php functionality can have wrong description.

[dimadeush]

Created issue for JetBrains as several products can be related - https://youtrack.jetbrains.com/issue/WI-80068/Wrong-php-documentation-inside-php-jar-plugin