Replace the implementation of maths in `UnsignedBigInteger`
and `SignedBigInteger` with LibTomMath. This gives benefits in terms of
less code to maintain, correctness and speed.
These changes also remove now-unsued methods and improve the error
propagation for functions allocating lots of memory. Additionally, the
new implementation is always trimmed and won't have dangling zeros when
exporting it.
The spec never mentions the possibility for the `hash` member of
`RsaHashedKeyAlgorithm` to be a string, it should be a `KeyAlgorithm`
object containing a `name` string member.
Spec: https://w3c.github.io/webcrypto/#dfn-RsaHashedKeyAlgorithm
The property was not accessible because it was not exposed to JS.
The issue was discovered while implementing `wrapKey` and `unwrapKey` in
the next commits.
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
The main motivation behind this is to remove JS specifics of the Realm
from the implementation of the Heap.
As a side effect of this change, this is a bit nicer to read than the
previous approach, and in my opinion, also makes it a little more clear
that this method is specific to a JavaScript Realm.
