Use {Service,Pod}Monitors from the Helm template

What does this MR do?

Replaces {Service,Pod}Monitor objects using objects from the Helm template. See commit messages for more information.

Related: gitlab-org/charts/gitlab!2376 (merged)

Test plan

Build the Operator manifest, configuring the image tag:

TAG=$(git branch --show-current) task build_operator

Install CR, enabling a PodMonitor and ServiceMonitor to test:

apiVersion: apps.gitlab.com/v1beta1
kind: GitLab
metadata:
  name: gitlab
  namespace: gitlab-system
spec:
  chart:
    version: "7.4.1"
    values:
      gitlab:
        gitaly:
          metrics:
            serviceMonitor:
              enabled: true
        sidekiq:
          metrics:
            podMonitor:
              enabled: true
      global:
        appConfig:
          initialDefaults:
            signupEnabled: false
        hosts:
          domain: mydomain.com
          externalIP: 1.2.3.4
      certmanager-issuer:
        email: mnielsen@gitlab.com

Ensure CR is Running:

$ kubectl get gl
NAME     STATUS    VERSION
gitlab   Running   7.4.1

Ensure objects exist:

$ kubectl get podmonitors
NAME             AGE
gitlab-sidekiq   8m50s

$ kubectl get servicemonitors
NAME                AGE
gitlab-gitaly       8m58s
gitlab-postgresql   8m58s
gitlab-redis        8m58s

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
• When ready for review, MR is labeled "~workflow::ready for review" per the Distribution MR workflow

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added (see !661 (comment 1602841777))
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.

Related issues

Closes #621 (closed)