Remove the /stats module

[rjsparks]

The /stats module as it currently exists is an attractive nuisance. It was intended to move the nice things that Jari has been maintaining into the datatracker, but the implementation didn't really achieve that.

As it is, what's presented ranges from incomplete to actually wrong.

We're going to remove it and schedule a new effort to build better statistics.

[rjsparks]

There are a few things, like the MeetingRegistration model, that should have been in other apps to begin with that will have to be moved.

[rjsparks]

Tero mentioned at https://mailarchive.ietf.org/arch/msg/tools-discuss/0Tw_KT4pYdUxoIf36p8yzn_bvEM that some parts of the existing implementation may remain useful, and we should review whether/what to move into the relevant apps while waiting for re-implementation.

[larseggert]

Are you still interested in a PR that rips out the document stats?

[rjsparks]

Yes, and the meeting stats. It would be best if the same PR moved the review-team stats into the review application.

[jennifer-richards]

The stats app still exists, but has been mostly removed. Closing this. The work to replace it is tracked as #8511