Add a devel document describing requirements for FT in Open MPI components

Update to the devel document for adding FT support to components. This
commit adds information about wait-sync, requests, BTLs, Files, RMA

Signed-off-by: Aurélien Bouteiller <bouteill@icl.utk.edu>

Complete the description of how to test for FT and how to update
OFI and UCX PML/MTL components

add figure to the devel FT doc

Move documentation in a subdir of contrib

Update the URL for ulfm-testings

Signed-off-by: Aurélien Bouteiller <bouteill@icl.utk.edu>

Author: abouteiller