Revert "base TaskTimeObserver: Record alloc stacks for investigation"

This reverts commit bc6d2a98.

Reason for revert: We have sufficient data to identify the problematic
TaskTimeObserver and this instrumentation causes problems
(crbug.com/345364940) so it should be reverted before the branch.

Original change's description:
> base TaskTimeObserver: Record alloc stacks for investigation
>
> TaskTimeObservers are being used-after-free. This investigates which
> component is not unregistering observers correctly. It will be
> reverted before beta, because unwinding the stack every
> TaskTimeObserver creation occurs is a bad idea.
>
> Bug: 337200890
> Change-Id: I6bbcde1d4ae098122f5f388765d42b1a3a3ffc51
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5596490


> Auto-Submit: Sean Maher <spvw@chromium.org>
> Commit-Queue: Sean Maher <spvw@chromium.org>
> Reviewed-by: Francois Pierre Doray <fdoray@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1310109}

Bug: 337200890, 345364940
Change-Id: I6e7ebf0a4ff95da6c9dc60ead605d25d72e4d1ef
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5605050
Commit-Queue: Francois Pierre Doray <fdoray@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1311700}