### 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_
func_name = lambda_function.name()
        url = "%s%s/functions/%s/invocations" % (forward_url, API_PATH_ROOT, func_name)
        copied_env_vars = lambda_function.envvars.copy()
        copied_env_vars["LOCALSTACK_HOSTNAME"] = config.HOSTNAME_EXTERNAL
        copied_env_vars["LOCALSTACK_EDGE_PORT"] = str(config.EDGE_PORT)
        headers = aws_stack.mock_aws_request_headers("lambda")
        headers["X-Amz-Region"] = lambda_function.region()
        headers["X-Amz-Request-Id"] = context.aws_request_id
        headers["X-Amz-Handler"] = lambda_function.handler
        headers["X-Amz-Function-ARN"] = context.invoked_function_arn
        headers["X-Amz-Function-Name"] = context.function_name
        headers["X-Amz-Function-Version"] = context.function_version
        headers["X-Amz-Role"] = lambda_function.role
        headers["X-Amz-Runtime"] = lambda_function.runtime
        headers["X-Amz-Timeout"] = str(lambda_function.timeout)
        headers["X-Amz-Memory-Size"] = str(context.memory_limit_in_mb)
        headers["X-Amz-Log-Group-Name"] = context.log_group_name
        headers["X-Amz-Log-Stream-Name"] = context.log_stream_name
        headers["X-Amz-Env-Vars"] = json.dumps(copied_env_vars)
        headers["X-Amz-Last-Modified"] = str(int(lambda_function.last_modified.timestamp() * 1000))
        headers["X-Amz-Invocation-Type"] = invocation_type
        headers["X-Amz-Log-Type"] = "Tail"
        if context.client_context:
            headers["X-Amz-Client-Context"] = context.client_context
        if context.cognito_identity:
            headers["X-Amz-Cognito-Identity"] = context.cognito_identity
        data = run_safe(lambda: to_str(event)) or event
        data = json.dumps(json_safe(data)) if isinstance(data, dict) else str(data)
        LOG.debug(
            "Forwarding Lambda invocation to LAMBDA_FORWARD_URL: %s", config.LAMBDA_FORWARD_URL