### 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)

"""Heartbeat DAG file processor and restart it if we are not done."""
        if not self._parent_signal_conn:
            raise ValueError("Process not started.")
        if self._process and not self._process.is_alive():
            self._process.join(timeout=0)
            if not self.done:
                self.log.warning(
                    "DagFileProcessorManager (PID=%d) exited with exit code %d - re-launching",
                    self._process.pid,
                    self._process.exitcode,
                )
                self.start()
        if self.done:
            return
        parsing_stat_age = time.monotonic() - self._last_parsing_stat_received_at
        if parsing_stat_age > self._processor_timeout.total_seconds():
            Stats.incr("dag_processing.manager_stalls")
            self.log.error(
                "DagFileProcessorManager (PID=%d) last sent a heartbeat %.2f seconds ago! Restarting it",
                self._process.pid,
                parsing_stat_age,
            )
            reap_process_group(self._process.pid, logger=self.log)
            self.start()
    def _sync_metadata(self, stat):