Re-enter runtime after resetting overlay from runtime (#6513)

This still assumes that the client did not start any transactions
before calling into runtime. This is the case for benchmarking
as long as either NativeWhenPossible or AlwaysWasm exection
strategy is chosen. Using any other will result in a panic.

substrate/primitives/state-machine/src/ext.rs

@@ -575,6 +575,9 @@ where
 		).expect(EXT_NOT_ALLOWED_TO_FAIL);
 		self.backend.wipe().expect(EXT_NOT_ALLOWED_TO_FAIL);
 		self.mark_dirty();
+		self.overlay
+			.enter_runtime()
+			.expect("We have reset the overlay above, so we can not be in the runtime; qed");
 	}
 
 	fn commit(&mut self) {
@@ -593,6 +596,9 @@ where
 			changes.main_storage_changes,
 		).expect(EXT_NOT_ALLOWED_TO_FAIL);
 		self.mark_dirty();
+		self.overlay
+			.enter_runtime()
+			.expect("We have reset the overlay above, so we can not be in the runtime; qed");
 	}
 
 	fn read_write_count(&self) -> (u32, u32, u32, u32) {