### 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)

test_dag_path = TEST_DAG_FOLDER / "test_scheduler_dags.py"
        async_mode = "sqlite" not in conf.get("database", "sql_alchemy_conn")
        log_file_loc = conf.get("logging", "DAG_PROCESSOR_MANAGER_LOG_LOCATION")
        try:
            os.remove(log_file_loc)
        except OSError:
            pass
        
        processor_agent = DagFileProcessorAgent(test_dag_path, 0, timedelta(days=365), [], False, async_mode)
        processor_agent.start()
        if not async_mode:
            processor_agent.run_single_parsing_loop()
        processor_agent._process.join()
        assert os.path.isfile(log_file_loc)