Convert delayed_bugs to bugs.

I have a suspicion that quite a few delayed bug paths are impossible to
reach, so I did an experiment.

I converted every `delayed_bug` to a `bug`, ran the full test suite,
then converted back every `bug` that was hit. A surprising number were
never hit.

The next commit will convert some more back, based on human judgment.

compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs

@@ -82,7 +82,7 @@ where
     let value = infcx.commit_if_ok(|_| {
         let ocx = ObligationCtxt::new(infcx);
         let value = op(&ocx).map_err(|_| {
-            infcx.dcx().span_delayed_bug(span, format!("error performing operation: {name}"))
+            infcx.dcx().span_bug(span, format!("error performing operation: {name}"))
         })?;
         let errors = ocx.select_all_or_error();
         if errors.is_empty() {

compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs

@@ -190,10 +190,9 @@ where
                 }
             }
             if !progress {
-                return Err(infcx.dcx().span_delayed_bug(
-                    span,
-                    format!("ambiguity processing {obligations:?} from {self:?}"),
-                ));
+                infcx
+                    .dcx()
+                    .span_bug(span, format!("ambiguity processing {obligations:?} from {self:?}"));
             }
         }