Add validation pattern to ProcessGroupIDPrefix

[johscheuer]

What would you like to be added/changed?

As mentioned in https://github.com/FoundationDB/fdb-kubernetes-operator/pull/1060/files#r821385897 we should consider adding a validation pattern to the ProcessGroupIDPrefix the suggestion was:

// +kubebuilder:validation:Pattern:=^[a-z0-9A-Z]([\-._a-z0-9A-Z])*[a-z0-9A-Z]$

We have to ensure that our validation pattern matches the validation pattern from Kubernetes: https://github.com/kubernetes/apimachinery/blob/master/pkg/util/validation/validation.go