WIP: Testing some `par_dispatch` stuff #5332

Job	Run time
CI-Rocm-HIP (hipcc, Release, hip, serial)	36m 35s
CI-Rocm-HIP (hipcc, Release, hip, mpi)	37m 8s
CI-Cuda-Host (g++, Release, cuda, serial)	47m 54s
CI-Rocm-HIP (hipcc, Debug, hip, serial)	1h 0m 42s
CI-Cuda-Host (g++, Release, cuda, mpi)	45m 37s
CI-Rocm-HIP (hipcc, Debug, hip, mpi)	1h 0m 31s
CI-Cuda-Host (g++, Release, host, serial)	12m 55s
CI-Cuda-Host (g++, Release, host, mpi)	12m 49s
CI-Cuda-Host (g++, Debug, cuda, serial)	1h 24m 13s
CI-Cuda-Host (g++, Debug, cuda, mpi)	1h 23m 46s
CI-Cuda-Host (g++, Debug, host, serial)	11m 51s
CI-Cuda-Host (g++, Debug, host, mpi)	12m 9s
CI-Cuda-Host (clang++-15, Release, cuda, serial)	30m 47s
CI-Cuda-Host (clang++-15, Release, cuda, mpi)	29m 32s
CI-Cuda-Host (clang++-15, Release, host, serial)	10m 46s
CI-Cuda-Host (clang++-15, Release, host, mpi)	10m 53s
CI-Cuda-Host (clang++-15, Debug, host, serial)	8m 29s
CI-Cuda-Host (clang++-15, Debug, host, mpi)	8m 31s
	10h 5m 8s

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