Test HTML fragment parsing algorithm in annotate-xml context with HTML encoding

[nox]

https://html.spec.whatwg.org/multipage/syntax.html#parsing-html-fragments
https://html.spec.whatwg.org/multipage/syntax.html#html-integration-point

Note: If the node in question is the context element passed to the HTML fragment parsing algorithm, then the start tag token for that element is the "fake" token created during by that HTML fragment parsing algorithm.

[gsnedders]

Does the test format even handle this? hmmm