### Apache Airflow version

main (development)

### What happened

asset compilation background thread is not killed when running `stop_airflow`  or `breeze stop`.

Webpack process takes a lot of memory, each `start-airflow` starts 4-5 of them.

After a few breeze start, we end up with 15+ webpack background processes that takes more than 20G RAM

### What you think should happen instead

`run_compile_www_assets` should stop when running `stop_airflow` from tmux. It looks like it spawn a `compile-www-assets-dev` pre-commit in a subprocess, that doesn't get killed when stopping breeze

### How to reproduce

```
breeze start-airflow --backend postgres --python 3.8 --dev-mode
# Wait for tmux session to start
breeze_stop

breeze start-airflow --backend postgres --python 3.8 --dev-mode
# Wait for tmux session to start
breeze_stop

# do a couple more if needed
```

Open tmux and monitor your memory, and specifically webpack processes.

### Operating System

Ubuntu 20.04.6 LTS

### Versions of Apache Airflow Providers

_No response_

### Deployment

Other

### Deployment details

_No response_

### Anything else

_No response_

### Are you willing to submit PR?

- [ ] 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)

#
#
"""Useful tools for running commands."""
from __future__ import annotations
import contextlib
import os
import re
import shlex
import stat
import subprocess
import sys
from distutils.version import StrictVersion
from functools import lru_cache
from pathlib import Path
from threading import Thread
from typing import Mapping, Union
from rich.markup import escape
from airflow_breeze.branch_defaults import AIRFLOW_BRANCH
from airflow_breeze.global_constants import APACHE_AIRFLOW_GITHUB_REPOSITORY
from airflow_breeze.utils.ci_group import ci_group
from airflow_breeze.utils.console import Output, get_console
from airflow_breeze.utils.path_utils import (
    AIRFLOW_SOURCES_ROOT,
    WWW_ASSET_COMPILE_LOCK,