FEAT-#285: Implement shared object storage for MPI backend #654

Job	Run time
lint (black)	7s
lint (flake8)	8s
test-ubuntu (backend ray, python 3.8)	6m 57s
test-ubuntu (backend mpi, python 3.8)	8m 18s
test-ubuntu (backend dask, python 3.8)	8m 37s
test-ubuntu (backend pymp, python 3.8)	8m 23s
test-ubuntu (backend pyseq, python 3.8)	7m 40s
test-ubuntu (backend ray, python 3.9)	1m 21s
test-ubuntu (backend mpi, python 3.9)	4m 56s
test-ubuntu (backend dask, python 3.9)	5m 32s
test-ubuntu (backend pymp, python 3.9)	2m 34s
test-ubuntu (backend pyseq, python 3.9)	4m 2s
test-windows (backend ray, python 3.8)	1s
test-windows (backend mpi, python 3.8)	35s
test-windows (backend dask, python 3.8)	26s
test-windows (backend pymp, python 3.8)	1s
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
	59m 44s

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