Make it possible to read MeshTags/MeshFunction from DOLFIN-Legacy with h5py and adios2 backend #5

Job	Run time
create-datasets / create-dolfin-data	58s
create-legacy-datasets / create-adios-data	59s
test-code (v2.10.2, ghcr.io/fenics/test-env:current-mpich)	11m 44s
test-code (v2.11.0, ghcr.io/fenics/test-env:current-openmpi)	11m 49s
test-code (v2.11.0, ghcr.io/fenics/test-env:current-mpich)	11m 48s
test-code (v2.10.2, ghcr.io/fenics/test-env:current-openmpi)	11m 48s
	49m 6s

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