* UX: Add a rake task to monitor progress for long rebakes
When doing mass rebaking, this task will print progress, speed and
expected time to completion (ETC) on a loop. It is meant for rebakes
that take several hours or days.
It will calculate a 10m moving average over the past 6 hours, and print
ETC accordingly.
It also shows Sidekiq stats in case Sidekiq jobs for rebaking were
enqueued separately, instead of using the rebake_posts tasks in this
file (which are 100% synchronous and do not touch Sidekiq at all).
NOTE: only the currently unbaked count at task start time is considered;
this is useful in live communities with lots of traffic, where new posts
might otherwise change the goal posts continuously.
* Satisfy stree