### 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_
import json
import logging
import os
import re
import signal
import subprocess
import sys
import threading
from typing import Dict, Optional
from requests.models import Response
from localstack import config
from localstack.constants import (
    HEADER_LOCALSTACK_EDGE_URL,
    HEADER_LOCALSTACK_REQUEST_URL,
    INTERNAL_AWS_ACCESS_KEY_ID,
    LOCALHOST,
    LOCALHOST_IP,
    LOCALSTACK_ROOT_FOLDER,
    LS_LOG_TRACE_INTERNAL,
    PATH_USER_REQUEST,
)
from localstack.dashboard import infra as dashboard_infra
from localstack.services import plugins
from localstack.services.cloudwatch.cloudwatch_listener import PATH_GET_RAW_METRICS
from localstack.services.generic_proxy import ProxyListener, modify_and_forward, start_proxy_server
from localstack.services.infra import PROXY_LISTENERS
from localstack.services.plugins import SERVICE_PLUGINS
from localstack.services.s3.s3_utils import uses_host_addressing
from localstack.services.sqs.sqs_listener import is_sqs_queue_url
from localstack.utils import persistence