Move the remaining LibJS primitive string users to UTF-16 views and
strings. Remove the primitive string UTF-8 accessors and byte-string
coercion paths so new callers cannot rely on the old storage model.
Keep primitive string storage in Utf16String and remove the UTF-8
storage path from PrimitiveString. ASCII strings still use compact
Utf16String ASCII storage, while UTF-16 becomes the only owned
representation.
This is an editorial change in the ECMA-402 spec. See:
https://github.com/tc39/ecma402/commit/a2beb66
We implement this change by introducing a virtual interface that all
Intl "service" objects must implement. A future patch will make use of
the virtualized RelevantExtensionKeys and ResolutionOptionDescriptors
accessors, and we will need to be able to use those slots from a generic
instance type.
These are going to be included in the ECMA-262 AOs once Temporal reaches
stage 4. There's no need to keep them in the Temporal namespace. Some
upcoming Temporal editorial changes will get awkward without this patch.
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
