### Apache Airflow version

2.4.1

### What happened

When there are large number of dag files, lets say 10K and each takes sometime to parse,  dag_parser doesnt pick any newly created files till all 10k files are finished parsing

`if not self._file_path_queue:
                self.emit_metrics()
                self.prepare_file_path_queue()`

Above logic only adds new files to queue when queue is empty

### What you think should happen instead

Every loop of dag processor should pick new files and add into file for parsing queue

### How to reproduce

_No response_

### Operating System

All

### Versions of Apache Airflow Providers

_No response_

### Deployment

Docker-Compose

### Deployment details

_No response_

### Anything else

_No response_

### Are you willing to submit PR?

- [X] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

nonlocal fake_processors
            processor = FakeDagFileProcessorRunner._create_process(*args, **kwargs)
            fake_processors.append(processor)
            return processor
        mock_processor.side_effect = fake_processor_
        manager = DagFileProcessorManager(
            dag_directory=dag_filepath,
            dag_ids=[],
            
            max_runs=100,
            processor_timeout=timedelta(seconds=5),
            signal_conn=child_pipe,
            pickle_dags=False,
            async_mode=True,
        )
        try:
            thread.start()
            
            manager._run_parsing_loop()
            exit_event.set()
        finally:
            logging.info("Closing pipes")
            parent_pipe.close()
            child_pipe.close()
            thread.join(timeout=1.0)
    @conf_vars({("core", "load_examples"): "False"})
    @mock.patch("airflow.dag_processing.manager.Stats.timing")
    def test_send_file_processing_statsd_timing(self, statsd_timing_mock, tmpdir):