This patch adds a workaround for a Swift issue where boolean bitfields
with getters and setters in SWIFT_UNSAFE_REFERENCE types are improperly
imported, causing an ICE.
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
