remove storages that only contain empty (#27452)

runtime/src/accounts_db.rs

@@ -4052,6 +4052,16 @@ impl AccountsDb {
                 self.accounts_index
                     .clean_dead_slot(*slot, &mut AccountsIndexRootsStats::default());
                 self.bank_hashes.write().unwrap().remove(slot);
+                // all storages have been removed from here and recycled or dropped
+                assert!(self
+                    .storage
+                    .map
+                    .remove(slot)
+                    .unwrap()
+                    .1
+                    .read()
+                    .unwrap()
+                    .is_empty());
             });
         }