perf(ext/url): use DOMString webidl instead of USVString

[AaronO]

Improves url parsing by ~20%:

• before: ~2450ns/parse
• after: ~1950ns/parse

This is safe since all these string values are immediately sent to the op-layer that uses v8::String::to_rust_string_lossy() with REPLACE_INVALID_UTF8 effectively doing the same transform as our USVString webidl converter

[lucacasonato]

The same probably applies to URLSearchParams too

[AaronO]

The same probably applies to URLSearchParams too

Only partially, since URLSearchParams has pure JS getters (see its get()/has()), so if we changed the converters but left the code otherwise as is, there would be a change in behaviour since it's possible to have a !== b yet USVString(a) === USVString(b)

So I decided to leave it as is, since we'll want to make other tweaks beyond just switching the webidl converter as for URL

[lucacasonato]

Makes sense. We could do it in the constructor though (that goes right into a parse op).