### 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_
"""Retrieve a field with the given key from the list of Records within 'event'."""
    try:
        return event["Records"][0][key]
    except KeyError:
        return None
def get_zip_bytes(function_code):
    """Returns the ZIP file contents from a FunctionCode dict.
    :type function_code: dict
    :param function_code: https://docs.aws.amazon.com/lambda/latest/dg/API_FunctionCode.html
    :returns: bytes of the Zip file.
    """
    function_code = function_code or {}
    if "S3Bucket" in function_code:
        s3_client = aws_stack.connect_to_service("s3")
        bytes_io = BytesIO()
        try:
            s3_client.download_fileobj(function_code["S3Bucket"], function_code["S3Key"], bytes_io)
            zip_file_content = bytes_io.getvalue()
        except Exception as e:
            s3_key = str(function_code.get("S3Key") or "")
            s3_url = f's3://{function_code["S3Bucket"]}{s3_key if s3_key.startswith("/") else f"/{s3_key}"}'
            raise ClientError(f"Unable to fetch Lambda archive from {s3_url}: {e}", 404)
    elif "ZipFile" in function_code:
        zip_file_content = function_code["ZipFile"]
        zip_file_content = base64.b64decode(zip_file_content)
    elif "ImageUri" in function_code:
        zip_file_content = None
    else:
        raise ClientError("No valid Lambda archive specified: %s" % list(function_code.keys()))