### 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)

"""Launch DagFileProcessorManager processor and start DAG parsing loop in manager."""
        mp_start_method = self._get_multiprocessing_start_method()
        context = multiprocessing.get_context(mp_start_method)
        self._last_parsing_stat_received_at = time.monotonic()
        self._parent_signal_conn, child_signal_conn = context.Pipe()
        process = context.Process(
            target=type(self)._run_processor_manager,
            args=(
                self._dag_directory,
                self._max_runs,
                self._processor_timeout,
                child_signal_conn,
                self._dag_ids,
                self._pickle_dags,
                self._async_mode,
            ),
        )
        self._process = process
        process.start()
        self.log.info("Launched DagFileProcessorManager with pid: %s", process.pid)
    def run_single_parsing_loop(self) -> None: