### Is there an existing issue for this?

- [X] I have searched the existing issues and read the documentation

### Question

A [recent commit](https://github.com/localstack/localstack/commit/f41b25cc8d68e97ce8eacd4374ded4a8072e50f6#diff-368e25a43c4a3200ecb9ae21e7b2a94da05d8eb24680bd6c2a37ee0e275bcd0aL67) scrapped the `{"features:initScripts":"initialized"}` feature that my team was relying on to bootstrap our development environment.

Basically we are putting a provisioning script in `/docker-entrypoint-initaws.d/` that installs Terraform and runs our Terraform definitions against `http://localhost:4566`. Then, the service that needs the AWS infrastructure has an entrypoint that polls `http://localstack:4566/health` and keeps looking for `{"features:initScripts":"initialized"}` in the response before attempting to actually start the service.

We found by trial and error that this was the most reliable way to bring up our stack, as opposed to looking for specific services to appear in the `/health` payload. However, now with this change we can't detect exactly when our Terraform provisioning finishes. It'd be great to get back that feature, or to have another way to detect when the LocalStack entrypoint has finished running the scripts in `/docker-entrypoint-initaws.d/`. For now we'll be sticking to `:0.12.19` instead of `:latest` as suggested.

Thank you.

### Anything else?

_No response_
from localstack.utils.common import (
    TMP_THREADS,
    ShellCommandThread,
    edge_ports_info,
    get_free_tcp_port,
    in_docker,
    is_linux,
    is_port_open,
    poll_condition,
    run,
    start_thread,
)
from localstack.utils.run import FuncThread
from localstack.utils.server import multiserver
from localstack.utils.testutil import is_local_test_mode
SIGNAL_HANDLERS_SETUP = False
READY_MARKER_OUTPUT = "Ready."
DEFAULT_BACKEND_HOST = "127.0.0.1"
PROXY_LISTENERS = {}
LOG = logging.getLogger(__name__)
INFRA_READY = threading.Event()
SHUTDOWN_INFRA = threading.Event()
config_listener.start_listener()
def patch_urllib3_connection_pool(**constructor_kwargs):
    """
    Override the default parameters of HTTPConnectionPool, e.g., set the pool size via maxsize=16
    """
    try:
        from urllib3 import connectionpool, poolmanager
        class MyHTTPSConnectionPool(connectionpool.HTTPSConnectionPool):