Improve accounting of long lived objects.

Subtract the objects that are unreachable and add back the ones that
are resurrected.  This likely doesn't matter in most cases but
if the GC is freeing a lot of cyclic garbage then we don't want to
over count the long lived objects.

Author: nascheme

Python/gc_free_threading.c

@@ -1230,6 +1230,9 @@ scan_heap_visitor(const mi_heap_t *heap, const mi_heap_area_t *area,
         else {
             worklist_push(&state->unreachable, op);
         }
+        // It is possible this object will be resurrected but
+        // for now we assume it will be deallocated.
+        state->long_lived_total--;
         return true;
     }
 
@@ -1911,6 +1914,7 @@ handle_resurrected_objects(struct collection_state *state)
                 _PyObject_ASSERT(op, Py_REFCNT(op) > 1);
                 worklist_remove(&iter);
                 merge_refcount(op, -1);  // remove worklist reference
+                state->long_lived_total++;
             }
         }
     }
@@ -2311,9 +2315,6 @@ gc_collect_internal(PyInterpreterState *interp, struct collection_state *state,
         }
     }
 
-    // Record the number of live GC objects
-    interp->gc.long_lived_total = state->long_lived_total;
-
     // Find weakref callbacks we will honor (but do not call them).
     find_weakref_callbacks(state);
     _PyEval_StartTheWorld(interp);
@@ -2336,6 +2337,9 @@ gc_collect_internal(PyInterpreterState *interp, struct collection_state *state,
     }
     _PyEval_StartTheWorld(interp);
 
+    // Record the number of live GC objects
+    interp->gc.long_lived_total = state->long_lived_total;
+
     if (err < 0) {
         cleanup_worklist(&state->unreachable);
         cleanup_worklist(&state->legacy_finalizers);