Introduce `Capacity.SchedulableDiskInBytes`
Introduce `Capacity.SchedulableDiskInBytes`

[#167467200]

Co-authored-by: Danail Branekov <43f82d874965b9fe2876a1a864fffde1e64d6143@gmail.com>

cloudfoundry-incubator/garden,cloudfoundry-incubator/garden