feat: add support for watchNamespace in kuberay-apiserver

[shaoqin2]

addresses #27

Add the support for kuberay-apiserver to also install role/rolebinding in a list of namespaces like kuberay-operator. Did it slightly differently from kuberay-operator so the rules section of the RBAC is shared instead of repeated to reduce the possible drift between the two files

I verified that this change does not change helm output for existing usecase

helm template test .  > prechange.yaml
helm template --set singleNamespaceInstall=true test .  > prechange_single.yaml

Applied this patch

helm template test .  > postchange.yaml
helm template --set singleNamespaceInstall=true test .  > postchange_single.yaml

$ diff prechange.yaml postchange.yaml
# expected, my helm .Release.Namespace is default so it's just being explicitly specified now
16a17
>   namespace: default
67a69
>   namespace: default
151a154,159


$ diff prechange_single.yaml postchange_single.yaml
16a17
>   namespace: default
67a69
>   namespace: default
151a154,159

And finally test the multi namespace feature work

helm template --set singleNamespaceInstall=true --set "watchNamespace={n1,n2}" test .

# Source: kuberay-apiserver/templates/role.yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
...
  name: kuberay-apiserver
  namespace: n1

# Source: kuberay-apiserver/templates/role.yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
...
  name: kuberay-apiserver
  namespace: n2

# Source: kuberay-apiserver/templates/rolebinding.yaml
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
...
  name: test-kuberay-apiserver
  namespace: n1

# Source: kuberay-apiserver/templates/rolebinding.yaml
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
...
  name: test-kuberay-apiserver
  namespace: n2