Operator manager needs liveness and readiness probes

The manager deployment for the operator currently has no liveness (is it running okay?) or readiness (is it ready to accept requests?) probes. We should add these because they let the user know that the operator is installed correctly and ready to start handling GitLab custom resource requests. We can add these to the manifest in config/manager.

Acceptance Criteria:

• GitLab operator manager deployment has one configured liveness probe
• GitLab operator manager deployment has one configured readiness probe

To do:

• Update controller runtime (!109 (merged))
• Add probes to the Operator deployment spec