### 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)

"""Have all files been processed at least once?"""
        return self._all_files_processed
    def terminate(self):
        """
        Send termination signal to DAG parsing processor manager
        and expect it to terminate all DAG file processors.
        """
        if self._process and self._process.is_alive():
            self.log.info("Sending termination message to manager.")
            try:
                self._parent_signal_conn.send(DagParsingSignal.TERMINATE_MANAGER)
            except ConnectionError:
                pass
    def end(self):
        """
        Terminate (and then kill) the manager process launched.
        :return:
        """
        if not self._process:
            self.log.warning("Ending without manager process.")
            return
        
        
        
        self._process.join(timeout=1.0)
        reap_process_group(self._process.pid, logger=self.log)
        self._parent_signal_conn.close()
class DagFileProcessorManager(LoggingMixin):