This introduces a new bit on the Isolate which tells whether promise
hooks, async event delegate or the debug delegate are enabled. Use
this new bit in places where we generally need to take the slow path
due to async instrumentation.

Bug: v8:7253, v8:7522, v8:8238
Change-Id: I8f34eeb9f8f7b56fcbb4deb59ac51b2d0907ff6c
Reviewed-on: https://chromium-review.googlesource.com/c/1296473
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56902}