prov/shm: SMR_MAX_PEERS too small for GH200

[angainor]

The definition of SMR_MAX_PEERS in prov/shm/src/smr_util.h

#define SMR_MAX_PEERS   256

results in segfaults when using lnx with shm on GH200 systems, which have 288 cores. Increasing this limit fixed the issue.

[aingerson]

@angainor Dang, I thought we had more time before we started seeing systems that would exceed 256! Thank you for letting us know. I have a new architecture design to add that would fix this.