These metrics can provide insights into ResourceClaim usage. The total count is
redundant because the apiserver also provides count of resources, but having it
in the same sub-system next to the count of allocated claims might be more
discoverable and helps monitor the controller itself.
The controller uses the exact same logic as the generic ephemeral inline volume
controller, just for inline ResourceClaimTemplate -> ResourceClaim.
In addition, it supports removal of pods from the ReservedFor field when those
pods are known to not need the claim anymore. At the moment, only this special
case is supported. Removal of arbitrary objects would imply granting full read
access to all types to determine whether a) an object is gone and b) if the
current incarnation is the one which is listed in ReservedFor. This may get
added later.
