### Is there an existing issue for this?

- [X] I have searched the existing issues

### Feature description

The use case I have in mind is to run Node 16.x Lambdas - the default container registry is `lambci/lambda` which is effectively abandoned. [Not even Node 14.x has been published](https://github.com/lambci/docker-lambda/pull/330). However, switching the registry over to [`amazon/aws-lambda-nodejs`](https://hub.docker.com/r/amazon/aws-lambda-nodejs) still fails to pull the container, since localstack is looking for the tag `nodejs16.x`. I'd like to be able to specify that if the runtime is `nodejs16.x` it just looks for tag `16`.

### 🧑‍💻 Implementation

_No response_

### Anything else?

_No response_
global THUNDRA_NODE_AGENT_INITIALIZED
    if not THUNDRA_NODE_AGENT_INITIALIZED:
        if _init_node_agent_configs() and _install_node_agent():
            THUNDRA_NODE_AGENT_INITIALIZED = True
def _get_latest_node_agent_version():
    try:
        return common.run("npm view @thundra/core version".split())
    except Exception as e:
        print("Unable to get latest version of Thundra Node agent: %s" % e)
        return None
def _init_node_agent_configs() -> bool:
    global THUNDRA_NODE_AGENT_VERSION
    global THUNDRA_NODE_AGENT_LOCAL_PATH
    global THUNDRA_NODE_AGENT_LOCAL_PATH_ON_HOST
    latest_version = _get_latest_node_agent_version()
    version = os.getenv("THUNDRA_AGENT_NODE_VERSION", latest_version)
    if not version:
        return False
    THUNDRA_NODE_AGENT_VERSION = version.strip()
    THUNDRA_NODE_AGENT_LOCAL_PATH = "%s/thundra/node/%s/" % (
        config.dirs.tmp,
        THUNDRA_NODE_AGENT_VERSION,
    )
    THUNDRA_NODE_AGENT_LOCAL_PATH_ON_HOST = "%s/thundra/node/%s/" % (
        config.dirs.functions,
        THUNDRA_NODE_AGENT_VERSION,
    )
    return True
def _install_node_agent() -> bool: