Group use statments

[burdges]

A larger project should group their use statements semantically with blank lines between groups, so std/core first, crates.io second, crates in same repo third, and imports from the same crate last, and alphabetical within groups.

use core::{..};
#[cfg(alloc)]
use alloc::{..}

use arrayref::ArrayRef;
use rand::thread_rng;

use sister_crate::foo;

use my_sub::bar;
use super::baz;

[calebcartwright]

Closing as a duplicate because there is already an existing group_imports configuration option, and the associated limitations/feature requests are discussed in several open issues (e.g. #4693, #4709)