### 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)

signal_conn=child_pipe,
            dag_ids=[],
            pickle_dags=False,
            async_mode=False,
        )
        with create_session() as session:
            self.run_processor_manager_one_loop(manager, parent_pipe)
            assert session.query(DbCallbackRequest).count() == 0
    @conf_vars(
        {
            ("core", "load_examples"): "False",
            ("scheduler", "standalone_dag_processor"): "True",
        }
    )
    def test_fetch_callbacks_for_current_dag_directory_only(self, tmpdir):
        """Test DagFileProcessorManager._fetch_callbacks method"""
        dag_filepath = TEST_DAG_FOLDER / "test_on_failure_callback_dag.py"
        callback1 = DagCallbackRequest(
            dag_id="test_start_date_scheduling",
            full_filepath=str(dag_filepath),
            is_failure_callback=True,
            processor_subdir=str(tmpdir),
            run_id="123",
        )
        callback2 = DagCallbackRequest(
            dag_id="test_start_date_scheduling",
            full_filepath=str(dag_filepath),
            is_failure_callback=True,
            processor_subdir="/some/other/dir/",
            run_id="456",