### 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_
run_safe,
    save_file,
    short_uid,
    to_bytes,
    to_str,
    unzip,
)
from localstack.utils.generic.wait_utils import wait_until
from localstack.utils.sync import poll_condition
from localstack.utils.testutil import (
    check_expected_lambda_log_events_length,
    create_lambda_archive,
    get_lambda_log_events,
)
from .functions import lambda_integration
from .lambda_test_util import concurrency_update_done, get_invoke_init_type, update_done
THIS_FOLDER = os.path.dirname(os.path.realpath(__file__))
TEST_LAMBDA_PYTHON = os.path.join(THIS_FOLDER, "functions/lambda_integration.py")
TEST_LAMBDA_PYTHON_ECHO = os.path.join(THIS_FOLDER, "functions/lambda_echo.py")
TEST_LAMBDA_PYTHON_VERSION = os.path.join(THIS_FOLDER, "functions/lambda_python_version.py")
TEST_LAMBDA_PYTHON_UNHANDLED_ERROR = os.path.join(
    THIS_FOLDER, "functions/lambda_unhandled_error.py"
)
TEST_LAMBDA_PYTHON3 = os.path.join(THIS_FOLDER, "functions/lambda_python3.py")
TEST_LAMBDA_INTEGRATION_NODEJS = os.path.join(THIS_FOLDER, "functions/lambda_integration.js")
TEST_LAMBDA_NODEJS = os.path.join(THIS_FOLDER, "functions/lambda_handler.js")
TEST_LAMBDA_HELLO_WORLD = os.path.join(THIS_FOLDER, "functions/lambda_hello_world.py")
TEST_LAMBDA_GOLANG_ZIP = os.path.join(THIS_FOLDER, "functions/golang/handler.zip")
TEST_LAMBDA_RUBY = os.path.join(THIS_FOLDER, "functions/lambda_integration.rb")
TEST_LAMBDA_DOTNETCORE2 = os.path.join(THIS_FOLDER, "functions/dotnetcore2/dotnetcore2.zip")