modify the used image gitlab-ci-local-util and wait-for-it

[pbuleon]

Is your feature request related to a problem? Please describe.
In release 4.58.0, 2 images are used by gitlab-ci-local :

• docker.io/firecow/gitlab-ci-local-util
• docker.io/sumina46/wait-for-it:latest
  If we use a private docker registry, with no access to docker.io, those images can't be pulled

Describe the solution you'd like
To be able to replace those images name using parameters or variables

Describe alternatives you've considered
Today I pull those images manually from my private registry and tag it with the expected name

Additional context

[ANGkeith]

regarding docker.io/firecow/gitlab-ci-local-util, it's already implemented via https://github.com/firecow/gitlab-ci-local/pull/1544/files
for docker.io/sumina46/wait-for-it:latest, we're open to contributions