Paired A/B at 448 ranks, three replicas per arm inside one allocation: with
no_locks=true the aggregated MPI_Win_create cost 1463 s against 1450 s
without it, the two ranges fully overlapping. A probe with MPI_Win_get_info
confirmed this Open MPI retains the hint, so the null result belongs to the
hint and not to a failed measurement; same_disp_unit was silently ignored.
Removes the cached MPI_Info handles and their helpers, and returns the four
PSCW win_create calls to MPI_INFO_NULL.
Stack-1
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