Move WindowOrWorkerGlobalScope's timers to modules/scheduler/

Nothing depends on them, and they are conceptually related to the
APIs that are already in modules/scheduler/.

Change-Id: I4c35acae0ddd0eb6c720da96e891bf32b73b6b98
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4557034


Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Commit-Queue: Nate Chapin <japhet@chromium.org>
Commit-Queue: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Scott Haseley <shaseley@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1148286}