[DomCrawler] fixed bug #12143
Clean up testing
Make fabbot happy
bug #13145 [DomCrawler] Fix behaviour with <base> tag (dkop, WouterJ)

This PR was merged into the 2.3 branch.

Discussion
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[DomCrawler] Fix behaviour with <base> tag

Finishes https://github.com/symfony/symfony/issues/12283

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #12283, #12143, #12144
| License       | MIT
| Doc PR        | -

Commits
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91447e8 Make fabbot happy
1d35e48 Clean up testing
61f22d7 [DomCrawler] fixed bug #12143
Fixes various phpdoc and coding standards.