### 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)

"""Start more processors if we have enough slots and files to process"""
        while self._parallelism - len(self._processors) > 0 and self._file_path_queue:
            file_path = self._file_path_queue.pop(0)
            
            if file_path in self._processors.keys():
                continue
            callback_to_execute_for_file = self._callback_to_execute[file_path]
            processor = self._create_process(
                file_path,
                self._pickle_dags,
                self._dag_ids,
                self.get_dag_directory(),
                callback_to_execute_for_file,
            )
            del self._callback_to_execute[file_path]
            Stats.incr("dag_processing.processes")
            processor.start()
            self.log.debug("Started a process (PID: %s) to generate tasks for %s", processor.pid, file_path)
            self._processors[file_path] = processor
            self.waitables[processor.waitable_handle] = processor
    def prepare_file_path_queue(self):
        """Generate more file paths to process. Result are saved in _file_path_queue."""
        self._parsing_start_time = time.perf_counter()
        
        
        file_paths_in_progress = self._processors.keys()
        now = timezone.utcnow()
        
        list_mode = conf.get("scheduler", "file_parsing_sort_mode")