Use new CLDeviceArray for testing with KernelAbstractions on CPU (when available) #497
Description
KernelAbstractions v0.10.0 (not released yet) will have an OpenCL POCLBackend with a CLDeviceArray array type. We should use it instead of pseudoGPUArray in testing, when available. For KernelAbstractions < v0.10 we should try to replace pseudoGPUArray by JLArrays.JLArray, which seems to have KA-support nowadays.
The POCLBackend may also be a very competitive alternative to our non-KernelAbstractions CPU code, we should benchmark it.