### 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_
lambda_client.get_function_configuration(
                FunctionName=func_name, Qualifier=first_ver["Version"]
            )["RevisionId"]
            == first_ver["RevisionId"]
        )
        # Normal published version without ProvisionedConcurrencyConfiguration
        assert get_invoke_init_type(lambda_client, func_name, first_ver["Version"]) == "on-demand"
        # Create ProvisionedConcurrencyConfiguration for this Version
        versioned_revision_id_before = lambda_client.get_function(
            FunctionName=func_name, Qualifier=first_ver["Version"]
        )["Configuration"]["RevisionId"]
        lambda_client.put_provisioned_concurrency_config(
            FunctionName=func_name,
            Qualifier=first_ver["Version"],
            ProvisionedConcurrentExecutions=1,
        )
        assert wait_until(concurrency_update_done(lambda_client, func_name, first_ver["Version"]))
        versioned_revision_id_after = lambda_client.get_function(
            FunctionName=func_name, Qualifier=first_ver["Version"]
        )["Configuration"]["RevisionId"]
        assert versioned_revision_id_before != versioned_revision_id_after
        assert (
            get_invoke_init_type(lambda_client, func_name, first_ver["Version"])
            == "provisioned-concurrency"
        )
        # $LATEST does *NOT* use provisioned concurrency
        assert get_invoke_init_type(lambda_client, func_name, "$LATEST") == "on-demand"
        # TODO: why is this flaky?
        # assert lambda_cl