Add GitLab Runner

Allows installing GitLab runner.

To test, use the following image and minimal values.yaml:

Image: registry.gitlab.com/gitlab-org/cluster-integration/cluster-applications/add-gitlab-runner:ff42e9ad1d4c22eff209015ffcd26bba7c0a7177

values.yaml:

gitlabUrl: https://gitlab.example.com
runnerRegistrationToken: <runner-token>

rbac:
  create: true

Related: gitlab-org/gitlab#35673 (closed)