Core: Tracking is no more!

The "Tracking" component has been a place for a random hodgepodge of bugs
that were designed to track things, but often had very poor ownership and
decision-making.  So we've removed it! I went through the open tracking
bugs and either closed them if they were no longer relevant, or moved them
to a more appropriate component.

You are welcome to keep using tracking bugs, but you should put them in a
component related to the work being tracked.

I would also encourage everyone to assign tracking bugs to the person who
is actually tracking the work (program manager, engineering manager, or
engineering lead). Having a tracking bug that is unassigned can be
confusing, because it's not clear who is actually responsible for *doing*
the tracking and followup. And that's a good way to remember to close out
tracking bugs when we're done with them!

As a reminder, the blocking relationship to use is that all the relevant
component bugs block the tracking bug, so the tracking bug depends on its
component work. Then when the

--BDS