Same fix as hive-operator#742 and listener-operator#418, applied to the two
workloads this chart ships.

serviceAccount.name had no effect: the ServiceAccount, the controller Deployment
and the CSI node driver DaemonSet all hardcoded <fullname>-serviceaccount, so the
value was silently ignored. They now resolve the name through
operator.serviceAccountName.

With serviceAccount.create=false the helper fell back to "default", giving pods
running as the namespace default ServiceAccount without the operator's
ClusterRole. It now requires serviceAccount.name, so the chart fails to render
instead of installing something that cannot work.

Rendered output is unchanged for the default values.

_helpers.tpl and serviceaccount.yaml are generated from operator-templating and
are ahead of the template until the matching change lands there.