Add optional envFrom.secretRef to deploment for credentials

[foot]

• Called "provider-credentials"
• It ends up in the helm-chart
• Name is not configurable.

$ make helm
test -s /Users/simon/weave/cluster-reflector-controller/bin/controller-gen && /Users/simon/weave/cluster-reflector-controller/bin/controller-gen --version | grep -q v0.13.0 || \
	GOBIN=/Users/simon/weave/cluster-reflector-controller/bin go install sigs.k8s.io/controller-tools/cmd/controller-gen@v0.13.0
/Users/simon/weave/cluster-reflector-controller/bin/controller-gen rbac:roleName=manager-role crd webhook paths="./..." output:crd:artifacts:config=config/crd/bases
/Users/simon/weave/cluster-reflector-controller/bin/kustomize build config/default | /Users/simon/weave/cluster-reflector-controller/bin/helmify -crd-dir charts/cluster-reflector-controller
# Warning: 'patchesStrategicMerge' is deprecated. Please use 'patches' instead. Run 'kustomize edit fix' to update your Kustomization automatically.

$ ag -C10 secretRef charts/cluster-reflector-controller/templates/deployment.yaml
48-          10 }}
49-        securityContext: {{- toYaml .Values.controllerManager.kubeRbacProxy.containerSecurityContext
50-          | nindent 10 }}
51-      - args: {{- toYaml .Values.controllerManager.manager.args | nindent 8 }}
52-        command:
53-        - /manager
54-        env:
55-        - name: KUBERNETES_CLUSTER_DOMAIN
56-          value: {{ quote .Values.kubernetesClusterDomain }}
57-        envFrom:
58:        - secretRef:
59-            name: provider-credentials
60-            optional: true
61-        image: {{ .Values.controllerManager.manager.image.repository }}:{{ .Values.controllerManager.manager.image.tag
62-          | default .Chart.AppVersion }}
63-        livenessProbe:
64-          httpGet:
65-            path: /healthz
66-            port: 8081
67-          initialDelaySeconds: 15
68-          periodSeconds: 20