Standalone smp-mem-bench executable that starts an in-process SMP server
and drives churn workloads, reporting GHC live-heap residency per
checkpoint after a forced major GC. Store selectable via BENCHSTORE
(pgmsg/pgjournal/journal).
Phases: plain, svc, svcrace, ntf, conc, svcsubs, getp, link, and leak
repros - stuck (delivery threads blocked forever on a full sndQ),
certchurn (serviceLocks/services grow per distinct service certificate),
and ntfexp (NtfStore keys retained after notifications expire).
