Can we add another module under
std::prelude and auto-use it on edition 2021?
I remember when we tried to include those traits into prelude but figured out that it's a breaking change. But now we're close to new edition, and auto-
use std::prelude::v1::*; is purely sugar added by the compiler.
One thing I can imagine that can be a problem is how we handle it on
cargo fix. I don't have much idea on this part.