Add GKE load balancer options for KAS service

What does this MR do?

Adds a couple of GKE specific load balancer options to expose the internal API outside of the cluster for GitLab.com

Related issues

gitlab-com/gl-infra/delivery#1623 (comment 529875258)

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 (with KAS_ENABLED = 1):
  • Before suggestions: https://gitlab.com/gitlab-org/charts/gitlab/-/pipelines/275142616
  • After suggestions: https://gitlab.com/gitlab-org/charts/gitlab/-/pipelines/275265289

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