Add DeviceRef::{has_unified_memory, recommended_max_working_set_size, max_tranfer_rate} (#186)
Add DeviceRef::{has_unified_memory, recommended_max_working_set_size, max_tranfer_rate} (#186)

* Add DeviceRef::{has_unified_memory, recommended_max_working_set_size, max_tranfer_rate}

- https://developer.apple.com/documentation/metal/mtldevice/3229025-hasunifiedmemory
- https://developer.apple.com/documentation/metal/mtldevice/2369280-recommendedmaxworkingsetsize
- https://developer.apple.com/documentation/metal/mtldevice/3114007-maxtransferrate

* Add DeviceRef::{has_unified_memory, recommended_max_working_set_size, max_tranfer_rate}

- https://developer.apple.com/documentation/metal/mtldevice/3229025-hasunifiedmemory
- https://developer.apple.com/documentation/metal/mtldevice/2369280-recommendedmaxworkingsetsize
- https://developer.apple.com/documentation/metal/mtldevice/3114007-maxtransferrate

Make DeviceRef::{recommended_max_working_set_size, max_transfer_rate} public
gfx-rs/metal-rs,fkaa/metal-rs