Revert "perf_hooks: make PerformanceObserver an AsyncResource"

This reverts commit 009e4182.

AFAIU the discussion at [1], PerformanceObserver had been made to
inherit from AsyncResource more or less as a band-aid in lack of a
better async_context candidate to invoke it in. In order to enable
access to AsyncLocalStores from PerformanceObservers invoked
synchronously through e.g. measure() or mark(), the current
async_context, if any, should be retained.

Note that this is a breaking change, but
- as has been commented at [1], PerformanceObserver being derived from
  AsyncResource is a "minor divergence from the spec" anyway,
- to my knowledge this is an internal implementation detail which has
  never been documented and
- I can't think of a good reason why existing PerformanceObserver
  implementations would possibly rely on it.

OTOH, it's probably worthwhile to not potentially invoke before() and
after() async_hooks for each and every PerformanceObserver notification.

[1] https://github.com/nodejs/node/pull/18789



Co-Authored-By: ZauberNerd <zaubernerd@zaubernerd.de>

PR-URL: https://github.com/nodejs/node/pull/36343


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>