Implement support for ResizableArrayBuffer/GrowableSharedArrayBuffer integration

[dschuff]

This proposal has been implemented in engines, and we should implement support for it in Emscripten. Specifically, that would mean switching to RAB/GSAB to back the typed heap views; with pthreads + growable memories, this would allow us to avoid checking for detachment on every heap reference. We might also want to do it with RAB in the non-threaded case (since the behavior of RAB matches wasm memories more closely) but that seems like less of a big deal.

There are a couple of open questions still in the spec (see discussion in the recent CG meeting but it probably doesn't block starting on this.

[sbc100]

Do we need a flag to enable it node and/or chrome for testing?

[dschuff]

For Chrome, I don't think so, it seems to be available without a flag. I'm not sure about node.