DoFn.teardown metrics are lost in Python SDK

If user code in DoFn.shutdown updates custom user metrics, those updates will not get registered e.g. counter increments are not registered.

Context: In FnApiRunner.run_stages, DoFn.teardown is called in worker_handler_manager.close_all, but this is called outside of the FnApiRunner.run_stage calls, so no metrics / monitoring info is retrieved there.