FIX - adopt new Diagnostic naming in newly migrated modules

FIX - ambiguous Diagnostic link in docs

UPDATE - rename diagnostic_items to IntoDiagnostic and AddToDiagnostic

[Gardening] FIX - formatting via `x fmt`

FIX - rebase conflicts. NOTE: Confirm wheather or not we want to handle TargetDataLayoutErrorsWrapper this way

DELETE - unneeded allow attributes in Handler method

FIX - broken test

FIX - Rebase conflict

UPDATE - rename residual _SessionDiagnostic and fix LintDiag link

compiler/rustc_trait_selection/src/errors.rs

@@ -1,4 +1,4 @@
-use rustc_errors::{fluent, IntoDiagnostic, ErrorGuaranteed, Handler};
+use rustc_errors::{fluent, ErrorGuaranteed, Handler, IntoDiagnostic};
 use rustc_macros::Diagnostic;
 use rustc_middle::ty::{PolyTraitRef, Ty, Unevaluated};
 use rustc_session::Limit;