Remove DiagnosticBuilder::delay_as_bug_without_consuming.

The existing uses are replaced in one of three ways.
- In a function that also has calls to `emit`, just rearrange the code
  so that exactly one of `delay_as_bug` or `emit` is called on every
  path.
- In a function returning a `DiagnosticBuilder`, use
  `downgrade_to_delayed_bug`. That's good enough because it will get
  emitted later anyway.
- In `unclosed_delim_err`, one set of errors is being replaced with
  another set, so just cancel the original errors.

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -361,7 +361,7 @@ pub fn unexpected_hidden_region_diagnostic<'tcx>(
             );
         }
         ty::ReError(_) => {
-            err.delay_as_bug_without_consuming();
+            err.downgrade_to_delayed_bug();
         }
         _ => {
             // Ugh. This is a painful case: the hidden region is not one

compiler/rustc_infer/src/infer/error_reporting/note.rs

@@ -281,7 +281,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             }
         };
         if sub.is_error() || sup.is_error() {
-            err.delay_as_bug_without_consuming();
+            err.downgrade_to_delayed_bug();
         }
         err
     }