### 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)

"""Sleeps until all the processors are done."""
        for processor in self._processors.values():
            while not processor.done:
                time.sleep(0.1)
    def _collect_results_from_processor(self, processor) -> None:
        self.log.debug("Processor for %s finished", processor.file_path)
        Stats.decr("dag_processing.processes")
        last_finish_time = timezone.utcnow()
        if processor.result is not None:
            num_dags, count_import_errors = processor.result
        else:
            self.log.error(
                "Processor for %s exited with return code %s.", processor.file_path, processor.exit_code
            )
            count_import_errors = -1
            num_dags = 0
        last_duration = last_finish_time - processor.start_time
        stat = DagFileStat(
            num_dags=num_dags,
            import_errors=count_import_errors,
            last_finish_time=last_finish_time,
            last_duration=last_duration,
            run_count=self.get_run_count(processor.file_path) + 1,
        )
        self._file_stats[processor.file_path] = stat
        file_name = os.path.splitext(os.path.basename(processor.file_path))[0].replace(os.sep, ".")
        Stats.timing(f"dag_processing.last_duration.{file_name}", last_duration)
    def collect_results(self) -> None: