### 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_
result = logs_client.describe_log_streams(logGroupName=log_group_name)["logStreams"]
            return len(result) > 0
        wait_until(_log_stream_available, strategy="linear")
        ls_result = logs_client.describe_log_streams(logGroupName=log_group_name)
        log_stream_name = ls_result["logStreams"][0]["logStreamName"]
        def _assert_log_output():
            log_events = logs_client.get_log_events(
                logGroupName=log_group_name, logStreamName=log_stream_name
            )["events"]
            return any(["starting wait" in e["message"] for e in log_events]) and any(
                ["done waiting" in e["message"] for e in log_events]
            )
        wait_until(_assert_log_output, strategy="linear")
    @pytest.mark.skip(reason="very slow (only execute when needed)")
    def test_lambda_provisioned_concurrency_moves_with_alias(
        self, lambda_client, logs_client, create_lambda_function, snapshot
    ):
        """
        create fn ⇒ publish version ⇒ create alias for version ⇒ put concurrency on alias
        ⇒ new version with change ⇒ change alias to new version ⇒ concurrency moves with alias? same behavior for calls to alias/version?
        """
        snapshot.add_transformer(snapshot.transform.lambda_api())
        func_name = f"test_lambda_{short_uid()}"