Request: replace use mod::submod::{self} with use mod::submod

[alex]

Sometimes, in the course of a refactoring one starts with use mod::submod::{a, b, c, self} and then you end up with only {self}.

I think in effectively 100% of cases it's desirable to remove the ::{self}.

I do not believe the existing options for import formatting do this.

[alex]

Nope, turns out rustfmt used to do this but it's not 100% semantically equivalent: #3568

Sorry about the noise!