Auto merge of #101558 - JhonnyBillM:session-diagnostic-to-diagnostic-handler-refactor, r=davidtwco

Move and rename `SessionDiagnostic` & `SessionSubdiagnostic` traits and macros

After PR #101434, we want to:
- [x] Move `SessionDiagnostic` to `rustc_errors`.
- [x] Add `emit_` methods that accept `impl SessionDiagnostic` to `Handler`.
- [x] _(optional)_ Rename trait `SessionDiagnostic` to `DiagnosticHandler`.
- [x] _(optional)_ Rename macro `SessionDiagnostic` to `DiagnosticHandler`.
- [x] Update Rustc Dev Guide and Docs to reflect these changes. https://github.com/rust-lang/rustc-dev-guide/pull/1460

Now I am having build issues getting the compiler to build when trying to rename the macro.

<details>
  <summary>See diagnostics errors and context when building.</summary>

```
error: diagnostics should only be created in `SessionDiagnostic`/`AddSubdiagnostic` impls
  --> compiler/rustc_attr/src/session_diagnostics.rs:13:10
   |
13 |   #[derive(DiagnosticHandler)]
   |            ^^^^^^^^^^^^^^^^^ in this derive macro expansion
   |
  ::: /Users/jhonny/.cargo/registry/src/github.com-1ecc6299db9ec823/synstructure-0.12.6/src/macros.rs:94:9
   |
94 | /         pub fn $derives(
95 | |             i: $crate::macros::TokenStream
96 | |         ) -> $crate::macros::TokenStream {
   | |________________________________________- in this expansion of `#[derive(DiagnosticHandler)]`
   |
note: the lint level is defined here
  --> compiler/rustc_attr/src/lib.rs:10:9
   |
10 | #![deny(rustc::diagnostic_outside_of_impl)]
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

```

And also this one:

```
error: diagnostics should only be created in `SessionDiagnostic`/`AddSubdiagnostic` impls
   --> compiler/rustc_attr/src/session_diagnostics.rs:213:32
    |
213 |         let mut diag = handler.struct_span_err_with_code(
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^^
```

> **Note**
> Can't find where this message is coming from, because you can see in [this experimental branch](https://github.com/JhonnyBillM/rust/tree/experimental/trying-to-rename-session-diagnostic-macro)  that I updated all errors and diags to say:
> error: diagnostics should only be created in **`DiagnosticHandler`**/`AddSubdiagnostic` impls
> and not:
> error: diagnostics should only be created in **`SessionDiagnostic`**/`AddSubdiagnostic` impls

</details>

I tried building the compiler in different ways (playing with the stages etc), but nothing worked.

## Question

**Do we need to build or do something different when renaming a macro and identifiers?**

For context, see experimental commit https://github.com/JhonnyBillM/rust/commit/f2193a98b44db3f2af77a878824b152cdf0d34a5 where the macro and symbols are renamed, but it doesn't compile.

1 files changed, 15 insertions, 15 deletions

diff --git a/compiler/rustc_interface/src/errors.rs b/compiler/rustc_interface/src/errors.rs
index 6a497aed4ab..097640f26c1 100644
--- a/compiler/rustc_interface/src/errors.rs
+++ b/compiler/rustc_interface/src/errors.rs
@@ -1,10 +1,10 @@
-use rustc_macros::SessionDiagnostic;
+use rustc_macros::Diagnostic;
 use rustc_span::{Span, Symbol};
 
 use std::io;
 use std::path::Path;
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(interface::ferris_identifier)]
 pub struct FerrisIdentifier {
     #[primary_span]
@@ -13,7 +13,7 @@ pub struct FerrisIdentifier {
     pub first_span: Span,
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(interface::emoji_identifier)]
 pub struct EmojiIdentifier {
     #[primary_span]
@@ -21,67 +21,67 @@ pub struct EmojiIdentifier {
     pub ident: Symbol,
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(interface::mixed_bin_crate)]
 pub struct MixedBinCrate;
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(interface::mixed_proc_macro_crate)]
 pub struct MixedProcMacroCrate;
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(interface::proc_macro_doc_without_arg)]
 pub struct ProcMacroDocWithoutArg;
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(interface::error_writing_dependencies)]
 pub struct ErrorWritingDependencies<'a> {
     pub path: &'a Path,
     pub error: io::Error,
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(interface::input_file_would_be_overwritten)]
 pub struct InputFileWouldBeOverWritten<'a> {
     pub path: &'a Path,
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(interface::generated_file_conflicts_with_directory)]
 pub struct GeneratedFileConflictsWithDirectory<'a> {
     pub input_path: &'a Path,
     pub dir_path: &'a Path,
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(interface::temps_dir_error)]
 pub struct TempsDirError;
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(interface::out_dir_error)]
 pub struct OutDirError;
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(interface::cant_emit_mir)]
 pub struct CantEmitMIR {
     pub error: io::Error,
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(interface::rustc_error_fatal)]
 pub struct RustcErrorFatal {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(interface::rustc_error_unexpected_annotation)]
 pub struct RustcErrorUnexpectedAnnotation {
     #[primary_span]
     pub span: Span,
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(interface::failed_writing_file)]
 pub struct FailedWritingFile<'a> {
     pub path: &'a Path,