FEAT-#285: Implement shared object storage for MPI backend #632

Job	Run time
lint (black)	8s
lint (flake8)	7s
test-ubuntu (backend ray, python 3.8)	6m 25s
test-ubuntu (backend mpi, python 3.8)	6m 6s
test-ubuntu (backend dask, python 3.8)	52m 10s
test-ubuntu (backend pymp, python 3.8)	6m 25s
test-ubuntu (backend pyseq, python 3.8)	6m 58s
test-ubuntu (backend ray, python 3.9)	6m 40s
test-ubuntu (backend mpi, python 3.9)	7m 37s
test-ubuntu (backend dask, python 3.9)	6m 25s
test-ubuntu (backend pymp, python 3.9)	6m 28s
test-ubuntu (backend pyseq, python 3.9)	7m 10s
test-windows (backend ray, python 3.8)	6m 15s
test-windows (backend mpi, python 3.8)	6m 13s
test-windows (backend dask, python 3.8)	6m 19s
test-windows (backend pymp, python 3.8)	6m 30s
test-windows (backend pyseq, python 3.8)	7m 19s
test-windows (backend ray, python 3.9)	6m 10s
test-windows (backend mpi, python 3.9)	9m 37s
test-windows (backend dask, python 3.9)	7m 43s
test-windows (backend pymp, python 3.9)	7m 52s
test-windows (backend pyseq, python 3.9)	5m 44s
	3h 2m 21s

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