async_hooks: prototype for v8 reimplementation of AsyncLocalStorage

This is an experiment in moving the machinery necessary for AsyncLocalStorage away from async_hooks and into V8 itself. The purpose is for better performance by entirely eliminating the unnecessary event sequence component of async_hooks and to enable sharing storage state with V8. This is very much a proof-of-concept in its current state. It's failing a bunch of tests still, that's expected, it's not complete yet.

Feel free to have a look and provide feedback on the direction if you like, just keep in mind this is not done yet.