[DomCrawler] Fixed filterXPath() chaining
bug #10207 [DomCrawler] Fixed filterXPath() chaining (robbertkl)

This PR was merged into the 2.3 branch.

Discussion
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[DomCrawler] Fixed filterXPath() chaining

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | debatable (see below)
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #10206
| License       | MIT
| Doc PR        |

As @stof mentions in #10206, each node in the Crawler can belong to a different \DOMDocument. Therefore, I've made each node do its own XPath, relative to itself, and add all the results to a new Crawler. This way, all resulting nodes are still part of their original \DOMDocument and thus can reach all of their parent nodes.

No current tests break on this change. I've added a new test for this case, by checking if the number of parents is correct after obtaining a node through chaining of `filterXPath()`.

Now for BC: I can think of a number of cases where this change would give a different result. However, it's debatable/unclear if:
- the old behavior was a bug in the first place (which would validate this change), or
- the old behavior was intended (which would make this a BC breaking change)

As an example, consider the following HTML:
```html
<div name="a"><div name="b"><div name="c"></div></div></div>
```
What would happen if we run this:
```php
echo $crawler->filterXPath('//div')->filterXPath('div')->filterXPath('div')->attr('name');
```
Aside from breaking reachability of the parent nodes by chaining, with the original code it would echo 'a'.
With this patch it would echo 'c', which, to me, makes more sense.

Commits
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43a7716 [DomCrawler] Fixed filterXPath() chaining