### 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)

headers = ["File Path", "PID", "Runtime", "# DAGs", "# Errors", "Last Runtime", "Last Run"]
        rows = []
        now = timezone.utcnow()
        for file_path in known_file_paths:
            last_runtime = self.get_last_runtime(file_path)
            num_dags = self.get_last_dag_count(file_path)
            num_errors = self.get_last_error_count(file_path)
            file_name = os.path.basename(file_path)
            file_name = os.path.splitext(file_name)[0].replace(os.sep, ".")
            processor_pid = self.get_pid(file_path)
            processor_start_time = self.get_start_time(file_path)
            runtime = (now - processor_start_time) if processor_start_time else None
            last_run = self.get_last_finish_time(file_path)
            if last_run:
                seconds_ago = (now - last_run).total_seconds()
                Stats.gauge(f"dag_processing.last_run.seconds_ago.{file_name}", seconds_ago)
            rows.append((file_path, processor_pid, runtime, num_dags, num_errors, last_runtime, last_run))
        
        rows = sorted(rows, key=lambda x: x[3] or 0.0)
        formatted_rows = []
        for file_path, pid, runtime, num_dags, num_errors, last_runtime, last_run in rows:
            formatted_rows.append(