Rollup merge of #104638 - Nilstrieb:macro-diagnostics, r=compiler-errors

Move macro_rules diagnostics to diagnostics module

This will make it easier to add more diagnostics in the future in a centralized place.

compiler/rustc_expand/src/expand.rs

@@ -1,7 +1,7 @@
 use crate::base::*;
 use crate::config::StripUnconfigured;
 use crate::hygiene::SyntaxContext;
-use crate::mbe::macro_rules::annotate_err_with_kind;
+use crate::mbe::diagnostics::annotate_err_with_kind;
 use crate::module::{mod_dir_path, parse_external_mod, DirOwnership, ParsedExternalMod};
 use crate::placeholders::{placeholder, PlaceholderExpander};