AMD GPU support

[fluidnumerics-joe]

I'm reaching out to see if there is interest in adding support for AMD GPUs. I'm working with Pawsey Supercomputing Centre in Australia to port some applications important for their user base and Segalign is on our list :)

I'm opening this to see if you'd have interest in merging this support into the main branch. I'd also like to discuss some approaches to provide this support without breaking support for users hat don't have ROCm on their own systems.