Need automated build for nephio-operator

[johnbelamaric]

While testing out the sandbox provisioning, it was failing during the "install nephio-operator". Turns out there was no image pushed :)

I manually build and pushed an image, but we should have it automated.

This one: https://github.com/nephio-project/nephio/tree/main/operators/nephio-controller-manager

[johnbelamaric]

/assign @radoslawc

The package looks for nephio-operator:latest: https://github.com/nephio-project/nephio-example-packages/blob/main/nephio-controllers/app/controller/deployment-controller.yaml#L82