v0.3.20 — fix feature-store serving preload (load exactly 10M keys)
Fixes the memtier_benchmark-playbook-feature-store-hash-10M-entities-50-features serving playbook: its -n allkeys preload used --key-maximum=10000000 and therefore loaded only 9,999,999 keys, failing the keyspacelen: 10000000 check and aborting the test. Bumped the preload to --key-maximum=10000001 (N+1) so it loads exactly 10,000,000 keys. clientconfig and the ingest playbook are unchanged. (#423)