Auto merge of #87668 - estebank:tweak-bound-output, r=oli-obk

Use note for pointing at bound introducing requirement

Modify output for pointing where a trait bound obligation is introduced in an E0277 from using a span label to using a note in order to always preserve order of the output:

Before:
```
error[E0277]: `<<Self as Case1>::A as Iterator>::Item` doesn't implement `Debug`
  --> $DIR/bounds-on-assoc-in-trait.rs:18:28
   |
LL |     type A: Iterator<Item: Debug>;
   |                            ^^^^^ `<<Self as Case1>::A as Iterator>::Item` cannot be formatted using `{:?}` because it doesn't implement `Debug`
   |
  ::: $SRC_DIR/core/src/fmt/mod.rs:LL:COL
   |
LL | pub trait Debug {
   | --------------- required by this bound in `Debug`
   |
   = help: the trait `Debug` is not implemented for `<<Self as Case1>::A as Iterator>::Item`
```
After:
```
error[E0277]: `<<Self as Case1>::A as Iterator>::Item` doesn't implement `Debug`
  --> $DIR/bounds-on-assoc-in-trait.rs:18:28
   |
LL |     type A: Iterator<Item: Debug>;
   |                            ^^^^^ `<<Self as Case1>::A as Iterator>::Item` cannot be formatted using `{:?}` because it doesn't implement `Debug`
   |
   = help: the trait `Debug` is not implemented for `<<Self as Case1>::A as Iterator>::Item`
note: required by a bound in `Debug`
  --> $SRC_DIR/core/src/fmt/mod.rs:LL:COL
   |
LL | pub trait Debug {
   | ^^^^^^^^^^^^^^^ required by this bound in `Debug`
```

0 files changed, 0 insertions, 0 deletions