This reverts commit 516d9068.

Reason for revert: Breaks layout tests:
https://ci.chromium.org/p/v8/builders/luci.v8.ci/V8-Blink%20Linux%2064/29444

See also:
https://v8.dev/docs/blink-layout-tests

Original change's description:
> Expose the number of microtasks from RunMicrotasks
> 
> This CL adds the number of processed microtasks to the tracing marker
> of RunMicrotasks, plus let RunMicrotasks return the number.
> 
> Bug: v8:7804, v8:8124
> Change-Id: Ie584e22964121fbda3a822379d760e7518fc54a7
> Reviewed-on: https://chromium-review.googlesource.com/c/1425277
> Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
> Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#59017}

TBR=bmeurer@chromium.org,tzik@chromium.org

Change-Id: I7db675dbbc496cc3c45220aa141252dd371d2780
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:7804, v8:8124
Reviewed-on: https://chromium-review.googlesource.com/c/1429859Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59018}