### 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_
import base64
import json
import logging
import os
import re
import shutil
import time
from io import BytesIO
from typing import Dict, TypeVar
import pytest
from botocore.exceptions import ClientError
from botocore.response import StreamingBody
from localstack.constants import LAMBDA_TEST_ROLE, TEST_AWS_ACCOUNT_ID
from localstack.services.awslambda import lambda_api
from localstack.services.awslambda.lambda_api import (
    LAMBDA_DEFAULT_HANDLER,
    get_lambda_policy_name,
    use_docker,
)
from localstack.services.awslambda.lambda_utils import (
    LAMBDA_RUNTIME_DOTNET6,
    LAMBDA_RUNTIME_DOTNETCORE31,