Condense use statements

[Nokel81]

It would be very nice if there was an easy way to condense all the use statements as much as possible. Such a feature would do change A) into B).

A)

use std::collections::HashMap;
use std::fs;
use std::fmt;
use std::fmt::{Display, Debug};

B)

use std::{collections::HashMap, fs, fmt::{self, Display, Debug}};

[DouglasLivingstone]

This will need support from rustfmt, there's discussion about adding a "merge_imports" feature here: rust-lang/rustfmt#3362