Port most html tests to html2

[compulim]

Changelog Entry

(No CHANGELOG as this is purely test infrastructure update.)

Description

Move most html tests to html2.

What left are tests containing permutation, that would take some brain juice to update them.

Specific Changes

• Move most html/* tests to html2/

• I have added tests and executed them locally
• I have updated CHANGELOG.md
• I have updated documentation

Review Checklist

This section is for contributors to review your work.

• Accessibility reviewed (tab order, content readability, alt text, color contrast)
• Browser and platform compatibilities reviewed
• CSS styles reviewed (minimal rules, no z-index)
• Documents reviewed (docs, samples, live demo)
• Internationalization reviewed (strings, unit formatting)
• package.json and package-lock.json reviewed
• Security reviewed (no data URIs, check for nonce leak)
• Tests reviewed (coverage, legitimacy)