Force eager JIT for several SYCL kernels with DPCPP

The GPU halo exchange pack/unpack kernels and force reduction kernels come in several flavours. Even hundreds of steps into a simulation, new flavours can be selected. This triggers JIT compilation of a newly selected flavour, which has the potential to disturb DLB, PME tuning, or benchmarking. Instead, we run all such kernels during setup so that JIT has already occured, so that artefacts do not appear.