Explicitly update or add doc comments denoting the unit of measurement

[atc0005]

Example:

check-vmware/internal/vsphere/datastores.go

Lines 33 to 43 in 7e988e8

	// DatastoreUsageSummary tracks usage details for a specific Datastore
	type DatastoreUsageSummary struct {
	Datastore mo.Datastore
	StorageRemainingPercent float64
	StorageUsedPercent float64
	StorageTotal int64
	StorageUsed int64
	StorageRemaining int64
	CriticalThreshold int
	WarningThreshold int
	}

I should note that each int64 field is using bytes as the unit of measurement (UOM). This matches the vSphere API:

freeSpace	xsd:long	Available space of this datastore, in bytes. The server periodically updates this value. It can be explicitly refreshed with the Refresh operation. This property is guaranteed to be valid only if accessible is true.

Other types (such as percentages used for WARNING and CRITICAL thresholds) should also be reviewed and annotated.