UCP: Add field_mask to ucp_params_t for ABI compatibility.
UCP: Add field_mask to ucp_params_t for ABI compatibility.

 Adding this mask would allow enlarging the size of the structure
without breaking ABI, since UCP could ignore fields not specified
by the mask.
 For now, field_mask is ingored.

sergsagal1/ucx_rocm,abouteiller/ucx,abouteiller/ucx,abouteiller/ucx,sergsagal1/ucx_rocm,sergsagal1/ucx_rocm,shssf/ucx,shssf/ucx,shssf/ucx,abouteiller/ucx