This implements the last WebCryptoAPI methods `wrapKey` and `unwrapKey`.
Most of the functionality is already there because they rely on
`encrypt` and `decrypt`. The only test failures are for `AES-GCM` which
is not implemented yet.
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
