### 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_
"""Returns directories used for when running localstack CLI commands from the host system. Unlike
        ``for_container``, these here need to be cross-platform. Ideally, this should not be needed at all,
        because the localstack runtime and CLI do not share any control paths. There are a handful of
        situations where directories or files may be created lazily for CLI commands. Some paths are
        intentionally set to None to provoke errors if these paths are used from the CLI - which they
        shouldn't. This is a symptom of not having a clear separation between CLI/runtime code, which will
        be a future project."""
        import tempfile
        from localstack.utils import files
        tmp_dir = os.path.join(tempfile.gettempdir(), "localstack-cli")
        cache_dir = (files.get_user_cache_dir()).absolute() / "localstack-cli"
        return Directories(
            static_libs=None,
            var_libs=None,
            cache=str(cache_dir),  
            tmp=tmp_dir,
            functions=None,
            data=os.path.join(tmp_dir, "state"),  
            logs=os.path.join(tmp_dir, "logs"),  
            config=None,  
            init=None,
        )
    def mkdirs(self):