Added resource-based metrics for storage groups/volumes and partition attach

[andy-maier]

For details, see the commit message.

Brief list of the new metrics:

zhmc_partition_storage_groups              Storage groups attached to the partition, as a comma-separated list

zhmc_storagegroup_type_int                 Storage group type as integer (0=fcp, 1=fc, 2=nvme, 99=unsupported value)
zhmc_storagegroup_fulfillment_state_int    Storage group fulfillment state as integer (0=complete, 1=pending, 2=pending-with-mismatches, 3=checking-migration, 4=incomplete, 99=unsupported value)
zhmc_storagegroup_shared                   Boolean indicating whether the storage group is shared (0=false, 1=true)
zhmc_storagegroup_max_partitions           Maximum number of partitions a storage group can be attached to

zhmc_storagevolume_fulfillment_state_int   Storage volume fulfillment state as integer (0=complete, 1=configuration-error, 2=deleting, 3=incomplete, 4=overprovisioned, 5=pending, 6=pending-with-mismatches, 99=unsupported value)
zhmc_storagevolume_usage_int               Usage of volume as integer (0=boot, 1=data, 2=not-applicable, 99=unsupported value)
zhmc_storagevolume_size_gib                Size of volume in GiB (0 for ECKD alias volumes)
zhmc_storagevolume_cylinders               Size of ECKD volume in cylinders (0 for ECKD alias volumes, not present for non-ECKD volumes)

[coveralls]

coverage: 39.074% (-1.5%) from 40.574% when pulling 883aec21fd6c5311c94198fe66b5c402c367ddc3 on andy/ccc-metrics into 35a223cad800a08ec14928d3e9672065cf5ce583 on master.

[andy-maier]

Fixed two issues.

[andy-maier]

Rebased the PR to master after merging other PRs.