~2% of the Speedometer 2.1 profile was just repeatedly performing the
shape transitions to add these two properties. We can avoid all that
work by caching a premade shape.
This avoids going through all the shape transitions when setting up the
most common form of ESFO.
This is extremely hot on Uber Eats, and this provides some relief.
In the very common case that no special constructor options are provided
for the Intl.Collator when calling localeCompare() on a string, we can
cache and reuse a default-constructed Intl.Collator, saving lots of time
and space.
This shaves a fair bit of load time off of https://wpt.fyi/ where they
use Array.prototype.sort() and localeCompare() to sort a big JSON thing.
Time spent in sort():
- Before: 1656 ms
- After: 135 ms
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