smyrna gvpr_select: use cgraph wrapper for allocation

smyrna gvpr_select: use cgraph wrapper for allocation

The lib/cgraph/alloc.h wrappers are similar to the older lib/common/memory.h
wrappers except (1) they are header-only and (2) they live in a directory
(cgraph) that is at the root of the dependency tree. The long term plan is to
replace all use of lib/common/memory.h with lib/cgraph/alloc.h.

The commit series ending in 78a0004fd0d1350f2c34e3a770d93032882706f7 previously
removed all uses of the lib/common/memory.h wrappers. But reverting
656a15f855a31acc6eeb162284b89ad3367253b9 brought another usage back in.