Previously we only matched against the first attribute with a given
local name. What we actually want to do is look at each attribute with
that local name in turn and only return false if none of them match.
Also remove a hack for HTML elements in HTML documents, where we would
refuse to match any namespaced attributes. This doesn't seem to be
based on the spec, but we had regressions without it, until now. :^)
Gets us 21 more WPT subtest passes.
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
