Support disabling certain components

Based on the values that are provided, there should be a validation if a resource should be created.

As an example, the self-signed certs job is only reconciled if certain values are configured.

Conversely, most of the other resources in the reconcile loop are reconciled always. This could cause problems if a user disabled a component, such as Registry. The reconcile loop would expect to find Registry-related objects in the Helm template, but they won't exist due to the values provided.

Details

Chart	Should	Can
Self-signed certs	y	y
Migrations	y	n
NGINX	y	y
Gitaly	y	y
MinIO	y	y
Redis	y	y
PostgreSQL	y	y
Pages	y	y
GitLab shell	y	n
Task-Runner	y	n
Exporter	n	n
Webservice	y	n
Sidekiq	y	n
Registry	y	n

Acceptance criteria

• The GitLab controller checks the Helm values first to confirm that a component should be included before reconciling it
• (Testing the above) Disabling a component such as Registry a.) does not crash the GitLab Operator with a nil error, and b.) does not attempt to reconcile Registry-related objects (can also test with other components)
• All components except for Webservice, Sidekikq, and Migrations can be disabled (!238 (merged))
• Webservice, Sidekiq and Migrations can be disabled (!287 (merged))