Make it possible to choose which Service will expose gitlab-shell

What does this MR do?

Use case: I want to expose my gitlab only through HTTP/HTTPS on internet and enable SSH only on internal service.

With this PR I can do that:

nginx-ingress:
  controller:
    service:
      enableShell: false
      internal:
        enableShell:  true

Tell me if I'm wrong.

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened