Add DiagCtxt::delayed_bug.

We have `span_delayed_bug` and often pass it a `DUMMY_SP`. This commit
adds `delayed_bug`, which matches pairs like `err`/`span_err` and
`warn`/`span_warn`.

compiler/rustc_query_system/src/query/plumbing.rs

@@ -431,17 +431,14 @@ where
                 // We have an inconsistency. This can happen if one of the two
                 // results is tainted by errors. In this case, delay a bug to
                 // ensure compilation is doomed.
-                qcx.dep_context().sess().dcx().span_delayed_bug(
-                    DUMMY_SP,
-                    format!(
-                        "Computed query value for {:?}({:?}) is inconsistent with fed value,\n\
+                qcx.dep_context().sess().dcx().delayed_bug(format!(
+                    "Computed query value for {:?}({:?}) is inconsistent with fed value,\n\
                         computed={:#?}\nfed={:#?}",
-                        query.dep_kind(),
-                        key,
-                        formatter(&result),
-                        formatter(&cached_result),
-                    ),
-                );
+                    query.dep_kind(),
+                    key,
+                    formatter(&result),
+                    formatter(&cached_result),
+                ));
             }
         }
     }