Add explicit_write suggestions for write!s with format args

[Alexendoo]

changelog: Add [explicit_write] suggestions for write!s with format args

Fixes #4542

writeln!(std::io::stderr(), "macro arg {}", one!()).unwrap();

Now suggests:

error: use of `writeln!(stderr(), ...).unwrap()`
  --> $DIR/explicit_write.rs:36:9
   |
LL |         writeln!(std::io::stderr(), "macro arg {}", one!()).unwrap();
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `eprintln!("macro arg {}", one!())`

---

r? @camsteffen (again, sorry 😛) for the FormatArgsExpn change

Before this change inputs_span returned a span pointing to just 1 in

macro_rules! one {
    () => { 1 };
}

`writeln!(std::io::stderr(), "macro arg {}", one!()).unwrap();`

And the source_callsite of that span didn't include the format string, it was just one!()

[Alexendoo]

@rustbot ready

Forgot to do that 👀

[camsteffen]

Thanks!

@bors r+

[bors]

📌 Commit 144b4a5 has been approved by camsteffen

[bors]

⌛ Testing commit 144b4a5 with merge 68b4498...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: camsteffen
Pushing 68b4498 to master...