[utils]: add script [field-per-job.sh]

This adds the script field-per-job.sh that allows to select the value of a given field for all jobs in a configuration.

To test

alias glciskd_util='docker run --entrypoint /bin/sh -v$(pwd):$(pwd) -w $(pwd) -e GLCISK="glcisk --gl-access-token <MY_ACCESS_TOKEN>" registry.gitlab.com/arvidnl/glci-swiss-army-knife:arvid_add_field_per_job_sh '
glciskd_util /glcisk/utils/field-per-job.sh tags

This should print all the tags for all the jobs defined in the configuration. For more info, see:

glciskd_util /glcisk/utils/field-per-job.sh --help