pub use counters::Count in ringbuf can't actually be used correctly

[hawkw]

The Count derive macro attempts to implement the counters::Count trait, so it doesn't work unless the crate in which the macro is expanded has a counters dependency. The ringbuf crate reexports the derive macro, which gives the impression that you can use that without having a direct dependency on counters...but if you do this, your code won't compile. Users still need to add a counters dependency as well, so the re-export doesn't actually do anything useful.

We should probably get rid of it, as it's really just a footgun (but like, a...foot rubber band gun; you can use it to shoot yourself in the foot, but the consequences of shooting yourself in the foot with it are "kind of annoying" but ultimately harmless).