Reuse HTML structuredClone for owning streams

[youennf]

#1271 is somehow duplicating https://html.spec.whatwg.org/multipage/structured-data.html#dom-structuredclone, except:

• structuredClone takes an options parameter instead of a transfer list.
• structuredClone is a visible function to JS

We should try to reuse more of HTML spec here

[MattiasBuelens]

Ideally, HTML would export an abstract op StructuredClone(value, transferList) and add it to this list, so it can be used by Streams. Then the user-land structuredClone() function would simply forward to that abstract op.