[2.1][DomCrawler] Fix relative path handling in links

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #7219
| License       | MIT
| Doc PR        | n/a

Added relative path canonicalization according to RFC 3986, section 5.2.4