chore: use rustfmt imports_granularity option (#17421)

Closes https://github.com/denoland/deno/issues/2699
Closes https://github.com/denoland/deno/issues/2347

Uses unstable rustfmt features. Since dprint invokes `rustfmt` we do not
need to switch the cargo toolchain to nightly. Do we care about
formatting stability of our codebase across Rust versions? (I don't)

cli/tools/coverage/mod.rs

@@ -24,7 +24,9 @@ use regex::Regex;
 use std::fs;
 use std::fs::File;
 use std::io::BufWriter;
-use std::io::{self, Error, Write};
+use std::io::Error;
+use std::io::Write;
+use std::io::{self};
 use std::path::PathBuf;
 use text_lines::TextLines;
 use uuid::Uuid;