Blender Git Loki

Cycles X: use less memory for float3 integrator state on GPU

Allocate different device_only_memory size depending if the device is CPU
or GPU, since for GPU we don't align to 16 bytes for SSE.

Also adds some sanity checks and ensure float3 is not used in device_vector
since it's incompatible for sharing data between CPU and GPU.

Differential Revision: https://developer.blender.org/D11913