[Pre-RFC] Bulk visibility syntax

I think this generally falls under the "alternative syntaxes" part of https://lang-team.rust-lang.org/frequently-requested-changes.html#fundamental-changes-to-rust-syntax.

Would this be terrible? No. But that's not the question. The big question is whether having two ways to do it is worse overall than just writing out pub a few more times. And to me, it's obvious that the answer is "no" there too. If you don't like typing it, use an IDE to add it to a bunch of stuff.

But I don't want to make people have a coding standards conversation about which they should use in a codebase. I don't want to have to discuss which one rustfmt should use. Etc.