feat: Add ragengine controller scaffolding code and chart

[Fei-Guo]

This PR adds the related scaffolding code/chart for the ragengine controller.

• Create a new directory in /cmd to hold the ragengine main package. Move workspace main package to /cmd/workspace
• Create pkg/controllers/ragengine_controller.go with minimum code required to run a controller.
• Add entries in Makefile for build binary and image.
• Add a new helm chart for installing ragengine controller deployment.
  -- The major change is that I add fullnameOverride: ragengine in values.yaml so that I can largely reuse the existing chart for workpsace.

Testing:

I can build kaito/ragengine:0.0.1 in my acr by running make docker-build-ragengine

helm install ragengine ./charts/kaito/ragengine --set image.repository=guofei.azurecr.io/kaito/ragengine --set 
 image.tag=0.0.1 --namespace ragengine --create-namespace
NAME: ragengine
LAST DEPLOYED: Thu Sep 19 10:31:04 2024
NAMESPACE: ragengine
STATUS: deployed
REVISION: 1
TEST SUITE: None

 k get pod -n ragengine
NAME                         READY   STATUS    RESTARTS   AGE
ragengine-5756f8f58f-smmhl   1/1     Running   0          73s

k logs ragengine-5756f8f58f-smmhl -n ragengine
I0919 17:31:14.940028       1 main.go:153] "starting manager"
2024-09-19T17:31:14Z    INFO    controller-runtime.metrics      Starting metrics server
2024-09-19T17:31:14Z    INFO    controller-runtime.metrics      Serving metrics server  {"bindAddress": ":8080", "secure": false}
2024-09-19T17:31:14Z    INFO    starting server {"name": "health probe", "addr": "[::]:8081"}
2024-09-19T17:31:14Z    INFO    Starting EventSource    {"controller": "ragengine", "controllerGroup": "kaito.sh", "controllerKind": "RAGEngine", "source": "kind source: *v1alpha1.RAGEngine"}
2024-09-19T17:31:14Z    INFO    Starting Controller     {"controller": "ragengine", "controllerGroup": "kaito.sh", "controllerKind": "RAGEngine"}
2024-09-19T17:31:16Z    INFO    Starting workers        {"controller": "ragengine", "controllerGroup": "kaito.sh", "controllerKind": "RAGEngine", "worker count": 5}