POC: Serverless uses separated internal docker registry module

[kwiatekus]

Description

Prototype changes is serverless necessary to integrate with docker registry separated to its own module.

Assumptions:

• Serverless operator communicates with docker registry operator via DockerRegistry CR (spec and status)
• Treat serverless to docker registry dependency as internal : this way we can ensure that serverless user experience remains unchanged:
  • Users do not have any extra configuration options wrt. internal docker registry other than they do now. (*)
  • Serverless users do not need to create/configure/delete DockerRegistry CR - serverless operator does it.
  • Docker registry operator should be installed by default to be ready to unstall/unistall docker registry resources
• Serverless on k3d doesn not need to install internal docker registry in order to use registry from k3d ( i.e this one initialised by kyma (alpha) deploy command). Document the need to patch coredns config map in such case

(*) Future configuration for docker registry storage should happen via DockerRegistry CR (volume size, nfs storage, s3-like store object, etc..).

Reasons
kyma-project/kyma#18555

Attachments
Depends on kyma-project/docker-registry#19

[kwiatekus]

Should be implemented only after this #941 is finished with negative result