Stack trace-friendly debug info for macros

This feels very similar to the problem where .unwrap() panics start their stack trace with implementation details of unwrap(): Better panic location reporting for `unwrap()` and friends

I don’t think it’s possible to solve both of these problems in general without some kind of explicit annotation, so I’m wondering if we can have a single attribute like #[hide_impl_in_panic_stacks] that “just works” for both macros and methods.