want a way to have `counters` derive counters for newtypes around integers with "reasonable" max values

See this comment I left on #2668

this is cute; I wonder if we might want the counters crate to have a macro or something for saying "yes, this looks like a u32, but it will always be in some range, so you can derive counters for it without having to worry"; elsewhere, I've tended to just use repr(N) enums for this sort of thing, like this thing:
https://github.com/oxidecomputer/hubris/blob/0d1ba0453a5d80470f07ea9949eb82bc3c291e01/drv/psc-seq-server/src/main.rs#L390-L403
but that then requires some weirdish boilerplate for converting between the enum and integers if you also want to index arrays or whatever.

very much not a blocker for this PR, but I wonder if we might throw together a little newtype-integer-counter derive or something that works like this.

Originally posted by @hawkw in https://github.com/oxidecomputer/hubris/pull/2668#discussion_r3937999238

Start with the counters crate and the discussion in issue #2668. Review the linked Hubris example in drv/psc-seq-server/src/main.rs around lines 390-403 to understand the existing repr(N) enum approach. Define the desired newtype-integer-counter behavior and how its max range should be specified before identifying the implementation and tests.