Refactor some of ASM and slot-stats functions

[tomerqodo]

Benchmark PR from agentic-review-benchmarks#4

[augmentcode]

🤖 Augment PR Summary

Summary: Refactors cluster/ASM initialization and cluster slot-data verification by moving shared logic into common entry points.

Changes:

• Routes CLUSTER MIGRATION and CLUSTER SYNCSLOTS handling through clusterCommand() instead of clusterCommandSpecial().
• Introduces clusterCommonInit() to initialize shared cluster state (slot-stats + ASM init) before clusterInit().
• Moves ASM lifecycle hooks (asmCron(), asmBeforeSleep()) out of the legacy cluster implementation into serverCron()/beforeSleep().
• Refactors startup data/config validation by centralizing verifyClusterConfigWithData() in cluster.c.
• Splits legacy-specific “claim unassigned slots” logic into clusterClaimUnassignedSlots().

Technical Notes: Startup slot verification now runs deletion/claim helpers, and slot-stats allocation moved from main() to the new common init path.

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[augmentcode]

Review completed. 2 suggestions posted.

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[augmentcode]

In verifyClusterConfigWithData(), clusterDeleteKeysInUnownedSlots() runs before clusterClaimUnassignedSlots(), but clusterDeleteKeysInUnownedSlots() doesn’t appear to exclude unassigned slots. This can cause keys in unassigned slots to be deleted on startup, preventing the later claim step and potentially causing data loss.

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[augmentcode]

clusterCommonInit() allocates server.cluster_slot_stats via plain malloc() (previously zmalloc() in main()), and then immediately dereferences it via resetClusterStats()/clusterSlotStatResetAll(). If allocation fails, this becomes a NULL deref, and it also bypasses Redis’ zmalloc accounting/oom behavior.

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