PriorityClassName for trident-controller and trident-operator

[KreshnikZ]

Issue description: Currently, the TridentOrchestrator does not provide a configuration option to set a PriorityClassName to the trident-controller and trident-operator deployments. In the case of the trident-controller this is especially important because without a running controller pod, most of the functions are not available, including volume mounting. As a consequence, the cluster cannot create new pods until the controller pod is running and because the controller does not have a high priority class, it could take a long time until a pod is scheduled. Cluster upgrades or disaster scenarios are the times where this would cause issues.

Feature request: Provide the ability to set the PriorityClassName for both the trident-controller and trident-operator deployments in the TridentOrchestrator.

Alterative feature: As an alternative, the trident-controller (and the trident-operator) should get the system-node-critical PriorityClassName, same as the DaemonSet.