nonminimal_bool lint for meta items

[clarfonthey]

I found myself ctrl-replacing a bunch of meta items in a file and ended up with a few that said cfg(not(not(...))). This is obviously wrong and it would be nice if we linted this somehow.

We could potentially extend this from just double negatives to include other expressions which include too many nots, like any(not(A), not(B), not(C), ...) -> not(all(A, B, C)).

[oli-obk]

I'm not sure if we can do this. Items that are cfg'ed out are invisible to clippy