Auto merge of #103217 - mejrs:track, r=eholk

Track where diagnostics were created.

This implements the `-Ztrack-diagnostics` flag, which uses `#[track_caller]` to track where diagnostics are created. It is meant as a debugging tool much like `-Ztreat-err-as-bug`.

For example, the following code...

```rust
struct A;
struct B;

fn main(){
    let _: A = B;
}
```
...now emits the following error message:

```
error[E0308]: mismatched types
 --> src\main.rs:5:16
  |
5 |     let _: A = B;
  |            -   ^ expected struct `A`, found struct `B`
  |            |
  |            expected due to this
-Ztrack-diagnostics: created at compiler\rustc_infer\src\infer\error_reporting\mod.rs:2275:31
```

compiler/rustc_parse/src/errors.rs

@@ -918,6 +918,7 @@ pub(crate) struct ExpectedIdentifier {
 }
 
 impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for ExpectedIdentifier {
+    #[track_caller]
     fn into_diagnostic(
         self,
         handler: &'a rustc_errors::Handler,
@@ -963,6 +964,7 @@ pub(crate) struct ExpectedSemi {
 }
 
 impl<'a, G: EmissionGuarantee> IntoDiagnostic<'a, G> for ExpectedSemi {
+    #[track_caller]
     fn into_diagnostic(
         self,
         handler: &'a rustc_errors::Handler,