be able to disable namespace watching by configuring the operator watches file

[jmazzitelli]

part of: kiali/kiali#7322

[jmazzitelli]

To test,

1. Build the helm charts: make build-helm-charts
2. See that the default behavior still generates the proper watches file. Run helm template --show-only templates/deployment.yaml _output/charts/kiali-operator-*.tgz and see the following in the Deployment yaml that is generated:

...
        - "--watches-file=./$(WATCHES_FILE)"
...
        - name: WATCHES_FILE
          value: "watches-k8s.yaml"
...

3. Now set a watches file: helm template --show-only templates/deployment.yaml --set watchesFile=watches-os-ns.yaml _output/charts/kiali-operator*.tgz and see that the env var value for WATCHES_FILE changed:

...
        - "--watches-file=./$(WATCHES_FILE)"
...
        - name: WATCHES_FILE
          value: "watches-os-ns.yaml"
...

4. You can install it to see it still works. Start a k8s cluster (like minikube) and run helm install --create-namespace -n kiali-operator --set image.tag=latest kiali-operator _output/charts/kiali-operator-*.tgz
5. At this point, confirm the operator starts up and is Running: kubectl get pods -n kiali-operator
6. See that the container args has --watches-files=./$(WATCHES_FILE):

$ kubectl get pod -n kiali-operator -l app.kubernetes.io/name=kiali-operator -o jsonpath='{..spec.containers..args[2]}{"\n"}'
--watches-file=./$(WATCHES_FILE)

7. You can uninstall after your test by running helm uninstall -n kiali-operator kiali-operator

[hhovsepy]

Verified in a scope of operator PR testing on remote OCP cluster.