Refactor GitLab Cells related configuration

Cells configuration in the Rails Application should look something like this:

  cell:
    enabled: boolean
    id: null
    database:
      skip_sequence_alteration: false
    topology_service:
      address: topology-service.gitlab.example.com:443
      ca_file: /home/git/gitlab/config/topology-service-ca.pem
      certificate_file: /home/git/gitlab/config/topology-service-cert.pem
      private_key_file: /home/git/gitlab/config/topology-service-key.pem

This would opening the current MRs:

• GitLab Rails application: !181708 (merged)
• GitLab Development Kit. See here Update: When we merged this, it broke old GitLab branches. So we are postponing this until %18.1
• Removing support of old Cells config format here: Something like !179385 (closed)

No default values are going to be changed

1. GitLab by default will keep the Cell disabled (cell.id is NULL and Topology Service is disabled).
2. GDK will have Cells enabled by default. Users can still disable it for Primary Cell: https://gitlab.com/gitlab-org/gitlab-development-kit/-/blob/main/doc/howto/cells.md?ref_type=heads#disabling-the-http-router

changed milestone to %17.9

added Category:Cell label

set weight to 2

added to epic &15279

added devopstenant scale groupcells infrastructure sectioninfrastructure platforms labels

marked this issue as blocking #487059 (closed)

mentioned in merge request !176157 (merged)

added maintenancerefactor label

added typemaintenance label

changed the description

assigned to @OmarQunsulGitlab

added workflowin dev label

id: 1

@OmarQunsulGitlab Does this mean cell.id has a default of 1 again ?

mentioned in commit 4a365f6e

mentioned in merge request !177988 (merged)

changed the description

mentioned in commit adfc0dbb

mentioned in commit d2630b6b

mentioned in commit 74508b63