errors: generate typed identifiers in each crate

Instead of loading the Fluent resources for every crate in
`rustc_error_messages`, each crate generates typed identifiers for its
own diagnostics and creates a static which are pulled together in the
`rustc_driver` crate and provided to the diagnostic emitter.

Signed-off-by: David Wood <david.wood@huawei.com>

compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs

@@ -149,7 +149,7 @@ impl<'tcx> LateLintPass<'tcx> for OpaqueHiddenInferredBound {
 struct OpaqueHiddenInferredBoundLint<'tcx> {
     ty: Ty<'tcx>,
     proj_ty: Ty<'tcx>,
-    #[label(specifically)]
+    #[label(lint_specifically)]
     assoc_pred_span: Span,
     #[subdiagnostic]
     add_bound: Option<AddBound<'tcx>>,