Setup Helm storage code and manifests

[pkosiec]

Description

The most important thing is that the point no 1 needs to be done ASAP to unblock other subtasks.

• Bootstrap Go code for the helm storage backends
  • Single entrypoint (directory in cmd)
  • Based on flags, a different storage backend gRPC server is run
  • Both servers (release + template) implement the same Storage Backend ProtoBuf interface (use already generated Go code)
  • Modify pipelines to build a single Docker image
• Add dedicated Helm chart and Hub manifests to install Helm storage backends
  • Single Helm chart, one deployment, two containers and two separate services
  • Update pipelines for releasing Helm charts
  • The implementation produces two TypeInstances for two storage backends (helm release backend + helm template backend) - define them
  • Write instruction on PR how to install such storage backend. It will be later reused in documentation
  • Base on secret storage backend, as this is pretty similar case (Configure Secret storage backend to be used with Local Hub #647)

Related issues

See epic #650

[pkosiec]

PRs:

• Bootstrap Helm storage backend Go app #669
• Add Helm chart for Helm backend storage #675
• Introduce Helm storage backends installation manifests hub-manifests#63