Registry: using upstream container

Add/Clean Registry sub-chart

This uses the upstream registry:2.6.2 container, and configures it for inter-communication with a deployed GitLab container.

Currently:

• Deployment with a default replicas count of 1.
• Contains a dedicated Ingress that can be enabled/disabled/configured separately from the top-level chart
• Can be entirely disabled via .Values.enabled (registry.enabled: false in parent)
• No defaults for Registry's storage: values, because they could collide with conflicting values when the YAML is merged. This must be configured by the user.

Requirements:

• external Secret for Registry's auth.token.rootcertbundle (registry['rootcertbundle'] = "/var/opt/gitlab/registry/gitlab-registry.crt" in Omnibus)
• If using TLS, secret containing valid SSL certificate for configured hostname.
• If using replicas: value greater than one, shared storage should be used (S3, shared PVC, et al).

I have tested this to be able to authenticate against my external GitLab Omnibus VM. While I could not get Minikube to allow communication for the GitLab instance to access the registry (thanks VirtualBox), I was able to confirm JWT authentication to function and be able to push/pull to verify ACLs (scopes) were functioning.