metrics: optional process_start_time
metrics: optional process_start_time

The process_start_time as registered by csi-lib-utils and thus
Kubernetes component base conflicts with the one from the Prometheus
Golang collector, leading to this error:

gathered metric family process_start_time_seconds has help "[ALPHA] Start time of the process since unix epoch in seconds." but should have "Start time of the process since unix epoch in seconds."

Allowing processes to control where they get the metric from solves
this conflict.

kubernetes-csi/csi-lib-utils,kubernetes-csi/csi-lib-utils,kubernetes-csi/csi-lib-utils