Draft: Update templates to use PostgreSQL decompositions

I have been testing with the following values for both the globally defined database and decomposed database environments:

Global database settings

global:
  hosts:
    # domain: ghickey.eks.helm-charts.win
    domain: ghickey.k8s-ft.win
  psql:
    host: pg-postgresql.pg.svc
    database: gitlabhq_production
    username: postgres
    preparedStatements: false
    password:
      secret: gitlab-postgres
      key: psql-password
postgresql:
install: false
certmanager-issuer:
email: ghickey@gitlab.com

Decomposed database settings

global:
  hosts:
    # domain: ghickey.eks.helm-charts.win
    domain: ghickey.k8s-ft.win
  psql:
    main:
      host: pg-main-postgresql.pg.svc
      database: gitlabhq_production
      username: postgres
      preparedStatements: false
      password:
        secret: gitlab-main-postgres
        key: psql-main-password
    ci:
      host: pg-ci-postgresql.pg.svc
      database: gitlabhq_production
      username: postgres
      preparedStatements: false
      password:
        secret: gitlab-ci-postgres
        key: psql-ci-password
postgresql:
install: false
certmanager-issuer:
email: ghickey@gitlab.com

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

Closes #3009