Use a better set of comparison/evaluation functions for deciding which connections to kill when OOS

Our existing OOS code kills low-priority OR connections. But really, we need to look at all connections that an adversary might be able to create (especially dir and exit connections), or else an adversary will be able to open a bunch of those, and force us to kill as many OR connections as they want.

This problem is the reason that DisableOOSCheck is now on-by-default.