Expose inter-process topology sharing

[HadrienG2]

Expose hwloc's support for sharing topologies between processes: https://hwloc.readthedocs.io/en/v2.9/group__hwlocality__shmem.html

[HadrienG2]

The suggested procedure is quite cumbersome, and implementing a high-level wrapper for it, at least on Linux, would likely be appreciated by interested users.