This adds a new operator JSCreatePromise, which currently allocates
a native JSPromise instance and initializes it to pending state.

In addition to that we introduce a new PromiseHookProtector, which
get's invalidated the first time someone enables the debugger or
installs a PromiseHook (via async_hooks for example). As long as
the protector is intact we lower AsyncFunctionPromiseCreate to
JSCreatePromise and AsyncFunctionPromiseRelease to a no-op in
optimized code.

This yields a speedup of roughly 33% on the benchmark mentioned
in the bug.

Bug: v8:7271, v8:7253
Change-Id: Ib5d219f2b6e052a7cc5e6ed5aa66dd3c8885a859
Reviewed-on: https://chromium-review.googlesource.com/883124
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50849}