### 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)

from setproctitle import setproctitle
from sqlalchemy.orm import Session
from tabulate import tabulate
import airflow.models
from airflow.callbacks.callback_requests import CallbackRequest, SlaCallbackRequest
from airflow.configuration import conf
from airflow.dag_processing.processor import DagFileProcessorProcess
from airflow.models import errors
from airflow.models.dag import DagModel
from airflow.models.dagwarning import DagWarning
from airflow.models.db_callback_request import DbCallbackRequest
from airflow.models.serialized_dag import SerializedDagModel
from airflow.stats import Stats
from airflow.utils import timezone
from airflow.utils.file import list_py_file_paths, might_contain_dag
from airflow.utils.log.logging_mixin import LoggingMixin
from airflow.utils.mixins import MultiprocessingStartMethodMixin
from airflow.utils.net import get_hostname
from airflow.utils.process_utils import (
    kill_child_processes_by_pids,
    reap_process_group,
    set_new_process_group,
)
from airflow.utils.session import NEW_SESSION, provide_session
from airflow.utils.sqlalchemy import prohibit_commit, skip_locked, with_row_locks
class DagParsingStat(NamedTuple):
    """Information on processing progress"""
    done: bool
    all_files_processed: bool
class DagFileStat(NamedTuple):