container-puller: use cwl-utils to automatically extract the container names

Shouldn't be too much work to modify https://github.com/common-workflow-language/cwl-utils/blob/main/cwl_utils/docker_extract.py to just print the container names instead of downloading them.

For a pure typescript approach, https://github.com/common-workflow-lab/cwl-ts-auto could be used ; though some [documents would need to be upgraded to CWL v1.2 first using one of the automated upgraders](https://github.com/common-workflow-lab/cwl-ts-auto#limitations).

Start by reading cwl_utils/docker_extract.py and the container-puller entry point in this repository. Run the existing extraction workflow to see how container references are handled, then verify that the completed change prints container names without downloading images; the issue also identifies cwl-ts-auto as an alternative for a TypeScript implementation.

Written by the indexing model from the issue text.