LibWeb: Implement HTMLInputElement type=url constraint validation

[sideshowbarker]

This change implements HTMLInputElement type=url constraint validation in such a way as to match the behavior in other existing engines — which is, however, very different from what the spec currently requires.

See https://github.com/whatwg/html/issues/11083 and see the additional test cases at https://github.com/web-platform-tests/wpt/pull/51011/files — and see Anne’s comment at https://github.com/web-platform-tests/wpt/pull/51011#issuecomment-2689983961.

For the record here: If we were to strictly implement the spec requirements as currently written, we’d end up reporting validation errors for a lot of cases that all other existing engines don’t report validation errors for. So, from a user point of view, it’d look to users as if our behavior is broken.

This therefore seems like a case where we’re better off just doing what other existing engines do.

[github-actions[bot]]

Your pull request has conflicts that need to be resolved before it can be reviewed and merged. Make sure to rebase your branch on top of the latest master.

[github-actions[bot]]

Your pull request has conflicts that need to be resolved before it can be reviewed and merged. Make sure to rebase your branch on top of the latest master.

[sideshowbarker]

I'll hold off merging this since there will be a conflict when #3775 is merged.

Merge conflict now resolved