### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

There appears to be an issue with this variable `export LAMBDA_KEEPALIVE_MS=1337`.
It's not picked up when you start `localstack start -d`

```shell
$ export LAMBDA_KEEPALIVE_MS=1000
$ env | grep LAMBDA_KEEPALIVE_MS
LAMBDA_KEEPALIVE_MS=1000
$ localstack start -d
$ docker inspect localstack_main -f '{{json .Config.Env}}' | grep LAMBDA_KEEPALIVE_MS
```

### Expected Behavior

It should be set in the container environment.

### How are you starting LocalStack?

With the `localstack` script

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

    docker run localstack/localstack

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

    awslocal s3 mb s3://mybucket


### Environment

```markdown
- OS: Windows (WSL)
- LocalStack: 2.2.1.dev20230731233910
```


### Anything else?

_No response_
PERSISTENCE = is_env_true("PERSISTENCE")
SNAPSHOT_LOAD_STRATEGY = os.environ.get("SNAPSHOT_LOAD_STRATEGY", "").upper()
SNAPSHOT_SAVE_STRATEGY = os.environ.get("SNAPSHOT_SAVE_STRATEGY", "").upper()
SNAPSHOT_FLUSH_INTERVAL = int(os.environ.get("SNAPSHOT_FLUSH_INTERVAL") or 15)
CLEAR_TMP_FOLDER = is_env_not_false("CLEAR_TMP_FOLDER")
TMP_FOLDER = os.path.join(tempfile.gettempdir(), "localstack")
VOLUME_DIR = os.environ.get("LOCALSTACK_VOLUME_DIR", "").strip() or TMP_FOLDER
if TMP_FOLDER.startswith("/var/folders/") and os.path.exists("/private%s" % TMP_FOLDER):
    TMP_FOLDER = "/private%s" % TMP_FOLDER
HOST_TMP_FOLDER = os.environ.get("HOST_TMP_FOLDER", TMP_FOLDER)
LS_LOG = eval_log_type("LS_LOG")
DEBUG = is_env_true("DEBUG") or LS_LOG in TRACE_LOG_LEVELS
DEVELOP = is_env_true("DEVELOP")
DEVELOP_PORT = int(os.environ.get("DEVELOP_PORT", "").strip() or DEFAULT_DEVELOP_PORT)
WAIT_FOR_DEBUGGER = is_env_true("WAIT_FOR_DEBUGGER")
USE_SSL = is_env_true("USE_SSL")
LEGACY_EDGE_PROXY = is_env_true("LEGACY_EDGE_PROXY")
LEGACY_S3_PROVIDER = os.environ.get("PROVIDER_OVERRIDE_S3", "") == "legacy"
STREAM_S3_PROVIDER = os.environ.get("PROVIDER_OVERRIDE_S3", "") == "stream"
FAIL_FAST = is_env_true("FAIL_FAST")
USE_SINGLE_REGION = is_env_true("USE_SINGLE_REGION")
TF_COMPAT_MODE = is_env_true("TF_COMPAT_MODE")
DEFAULT_ENCODING = "utf-8"
DOCKER_SOCK = os.environ.get("DOCKER_SOCK", "").strip() or "/var/run/docker.sock"
DOCKER_FLAGS = os.environ.get("DOCKER_FLAGS", "").strip()
DOCKER_CMD = os.environ.get("DOCKER_CMD", "").strip() or "docker"
LEGACY_DOCKER_CLIENT = is_env_true("LEGACY_DOCKER_CLIENT")
PORTS_CHECK_DOCKER_IMAGE = os.environ.get("PORTS_CHECK_DOCKER_IMAGE", "").strip()
FORWARD_EDGE_INMEM = True
def is_trace_logging_enabled():