Idle time work should only do work during idle time. Starting a timer as we come out of idle will add work that contends with non-idle activity.
<rdar://problem/111962239>
Pull request: https://github.com/WebKit/WebKit/pull/15671
Committed 265884@main (7e5881c7a9e7): <https://commits.webkit.org/265884@main> Reviewed commits have been landed. Closing PR #15671 and removing active labels.