Rollup merge of #119538 - nnethercote:cleanup-errors-5, r=compiler-er…

…rors

Cleanup error handlers: round 5

More rustc_errors cleanups. A sequel to rust-lang/rust#119171.

r? ````@compiler-errors````

src/errors.rs

@@ -119,12 +119,12 @@ impl<G: EmissionGuarantee> IntoDiagnostic<'_, G> for TargetFeatureDisableOrEnabl
             fluent::codegen_gcc_target_feature_disable_or_enable
         );
         if let Some(span) = self.span {
-            diag.set_span(span);
+            diag.span(span);
         };
         if let Some(missing_features) = self.missing_features {
             diag.subdiagnostic(missing_features);
         }
-        diag.set_arg("features", self.features.join(", "));
+        diag.arg("features", self.features.join(", "));
         diag
     }
 }