As described in https://crbug.com/1287476, the fact that the
AsyncEventDelegate is currently implemented on top of the PromiseHooks
causes performance problems and makes it difficult to reason about the
exact (observed) semantics; this is because for this we intercept every
JSPromise creation (via PromiseHook::kInit) and walk the synchronous
stack at that point to see if we find one of Promise#then(),
Promise#catch() or Promise#finally() on the stack. And if we do so, we
report that to the AsyncEventDelegate (which is implemented in the
inspector and will then do the async stack/stepping logic on top).

This CL introduces dedicated instrumentation for Promise#then(), which
is also called from Promise#catch() and Promise#finally(), and uses that
instrumentation for the purpose of the AsyncEventDelegate. It also
adjusts the stack walk to not always walk the full stack (which might
lead to wrong results when calls to Promise#then(), which itself can
call back into user JavaScript, are found deeper in the stack), but
instead only check the top-most builtin frames and whatever user
JavaScript frame is underneath it.

On the standalone.js (from https://crbug.com/1287476#c1), when run with
the DevTools default of maxDepth=200, we go from around 4.00ms to around
0.36ms. For everything that does not call Promise#then() - either
explicitly or implicitly - or `await`s, there's now no observable
performance impact of turning on the AsyncEventDelegate.

Bug: chromium:1280519
Fixed: chromium:1287476
Change-Id: I4911bed146381fc46cfeefb763d6dfc32e8f6071
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3386379
Auto-Submit: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78640}