Which has an optmization if both size of the string being passed
through are FlyStrings, which actually ends up being the case
in some places during selector matching comparing attribute names.
Instead of maintaining more overloads of
Infra::is_ascii_case_insensitive_match, switch
everything over to equals_ignoring_ascii_case instead.
When constructing an entry list, XHR::FormDataEntry is created
manually and appended to the entry list instead of using the
spec-defined method of creating an entry.
Previously, the list was copied when constructing the FormData object,
then the original list was passed to the event, meaning any changes to
the list that happened within the event would not be reflected outside
of it.
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
