Add support for bf16 for afoneapi/afcuda

Add suppor for bf16 datatype
https://github.com/arrayfire/arrayfire/blob/master/include/af/defines.h
for :
- afcuda/nvidia gpus
https://sources.debian.org/src/nvidia-cuda-toolkit/11.2.2-3%2Bdeb11u3/arm64/cuda_cudart/targets/sbsa-linux/include/cuda_bf16.hpp/#L126

- 4th gen intel CPUs (SaphirreRapids) with avx512bf16 / AMX

Description
===========
* Additional information about the feature you would like to add
bf16 datatype
* What problem are you trying to solve?
computation at bf16 precision
* (Optional) API of new function
No new API, just a new type in defines.h

* (Optional)Are there other libraries that implement this feature?
pytorch, numpy, oneDNN, ...