[New feature] Detect useless usage of Format.fprintf

Can a rule to warn about the following kind of ``Format.fprintf`` usages be useful?

```
let f fmt s i =
  ...
  Format.fprintf fmt "Hi!";
  Format.fprintf fmt "%s" s
  (* Use instead: Format.pp_print_string fmt s *)
  Format.fprintf fmt "%d" i
  (* Use instead: Format.pp_print_int fmt i *)
```
