Try out PoCL-R

This feature of PoCL makes it possible to offload to multiple servers, see https://github.com/pocl/pocl/pull/1621#issuecomment-2415865032. That could be an interesting approach to distributing code, although I fear that our current SPMD-style kernels are written with local GPUs in mind and thus won't scale well to a distributed execution environment.

(I know OpenCL.jl isn't the best place to keep track of this, but it's close enough, and issues on pocl_jll.jl have no visibility.)