[interop layer] Add AFD parsing and tests to interop

[eric-gade]

Description

We need to rewrite the AFD parser in JS and add to the interop layer. Additionally, we should transliterate the corresponding parser tests.

Acceptance criteria

• [ ] AFD parsing is handled by the interop layer
  • [ ] the bug identified in #1830 is addressed
• [ ] Tests within the interop layer capture the same capabilities as the current tests
• [ ] PHP-side templates / classes are updated to use parsed markup from the interop, rather than creating markup themselves

[colinmurphy01]

@eric-gade we're temporarily assigning this you for this sprint, we can regroup when you're back.