OSHMEM: add support for MPI collectives

oshmem collective can select MPI collectives modules as provider.

Developed by Elena, reviewed by Miked

cmr=v1.7.5:reviewer=ompi-rm1.7
OSHMEM: ikrit optimization

no need pre-register heap if MXM/ud is used
fixed by Alex, reviewed by Miked

cmr=v1.7.5:reviewer=ompi-rm1.7