☂ PodGangSet and PodGang operator

[unmarshall]

Create an operator to manage the lifecycle of PodGangSet and PodGang custom resources.

• Create the project structure for operator go-submodule
• Define APIs for custom resources
• Add hack/scripts to automate:
  • Formatting
  • Linting
  • Code generation (including CRD generation)
  • Kind cluster setup with local docker registry
  • Generate API reference documentation
  • Automatically prepend license for all source files
  • Unit tests
  • Integration tests
• Define configuration for the controller-manager and the respective controllers
• Setup webhook and metrics endpoints
• Create validation and defaulting webhook #10
• Setup readyz and healthz endpoints and their respective handlers
• Create main and setup signal handling, logging and initialisation of the controller-manager.
• Setup Dockerfile
• Setup skaffold