FEAT-#285: Implement shared object storage for MPI backend #651

Job	Run time
lint (black)	15s
lint (flake8)	10s
test-ubuntu (backend ray, python 3.8)	7m 1s
test-ubuntu (backend mpi, python 3.8)	7m 14s
test-ubuntu (backend dask, python 3.8)	7m 13s
test-ubuntu (backend pymp, python 3.8)	7m 2s
test-ubuntu (backend pyseq, python 3.8)	7m 0s
test-ubuntu (backend ray, python 3.9)	7m 6s
test-ubuntu (backend mpi, python 3.9)	7m 13s
test-ubuntu (backend dask, python 3.9)	7m 12s
test-ubuntu (backend pymp, python 3.9)	7m 3s
test-ubuntu (backend pyseq, python 3.9)	7m 2s
test-windows (backend ray, python 3.8)	1s
test-windows (backend mpi, python 3.8)	6m 56s
test-windows (backend dask, python 3.8)	7m 12s
test-windows (backend pymp, python 3.8)	5m 54s
test-windows (backend pyseq, python 3.8)	1s
test-windows (backend ray, python 3.9)	1s
test-windows (backend mpi, python 3.9)	1s
test-windows (backend dask, python 3.9)	1s
test-windows (backend pymp, python 3.9)	1s
test-windows (backend pyseq, python 3.9)	1s
	1h 31m 40s

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