Auto merge of #8365 - Alexendoo:explicit-write-suggestion, r=camsteffen

Auto merge of #8365 - Alexendoo:explicit-write-suggestion, r=camsteffen

Add `explicit_write` suggestions for `write!`s with format args

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

Fixes #4542

```rust
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

```rust
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!()`