Rollup merge of #99480 - miam-miam100:arg-format, r=oli-obk

Diagnostic width span is not added when '0$' is used as width in format strings

When the following code is run rustc does not add diagnostic spans for the width argument. Such spans are necessary for a clippy lint that I am currently writing.

```rust
println!("Hello {1:0$}!", 5, "x");
//                 ^^
// Should have a span here
```

compiler/rustc_builtin_macros/src/format.rs

@@ -485,7 +485,7 @@ impl<'a, 'b> Context<'a, 'b> {
             if let Some(span) = fmt.width_span {
                 let span = self.fmtsp.from_inner(InnerSpan::new(span.start, span.end));
                 match fmt.width {
-                    parse::CountIsParam(pos) if pos > self.num_args() => {
+                    parse::CountIsParam(pos) if pos >= self.num_args() => {
                         e.span_label(
                             span,
                             &format!(