Add cluster benchmark support to Resp.benchmark

[vazois]

Summary

Adds a --cluster-bench mode to Resp.benchmark for benchmarking Garnet cluster deployments.

Features

• Cluster topology discovery: Automatically discovers shards, slot ranges, and replicas via CLUSTER NODES
• Two architectures:
  • Sharded mode: Dedicated threads per shard with slot-aware key generation
  • Worker pool mode (--pool): Workers distribute operations across all shards
• Offline & online modes: Pre-generated RESP buffers (offline) or on-the-fly generation (online)
• Broadcast mode (--broadcast): Pipeline requests to all shards before completing, maximizing overlap
• Mixed workload: --replica-ops-percent pipelines writes to primary + reads to replica in parallel
• Multiple client types: LightClient, GarnetClientSession, GarnetClient, SERedis
• Operations: GET, SET, MGET, MSET, INCR, DEL
• Metrics: Kops/sec, data GB/s, wire Gbps, per-shard breakdown, latency percentiles (p50-p99.9), hit rates, primary/replica throughput split

Key files

• ClusterBench/ClusterWorkloadDriver.cs — Orchestrator (topology, load, config, final reports)
• ClusterBench/ClientRequestProvider.cs — RESP command generation, routing
• ClusterBench/ClientRequestProvider.{Offline,Online,WorkerPool}.cs — Mode-specific execution
• ClusterBench/Worker.cs — Worker thread orchestration
• ClusterBench/SlotKeyGenerator.cs — Slot-aware key generation with hash-tag prefixes
• ClusterBench/ClusterManager.cs — Topology discovery and slot mapping

Usage examples

# Basic cluster benchmark (3 shards, 8 threads/shard, offline)
Resp.benchmark --cluster-bench -h 127.0.0.1 -p 7000 --op SET -t 8 --dbsize 65536

# Worker pool with broadcast
Resp.benchmark --cluster-bench -h 127.0.0.1 -p 7000 --op GET -t 16 --dbsize 65536 --pool --broadcast

# Mixed workload with replicas (50% reads to replica)
Resp.benchmark --cluster-bench -h 127.0.0.1 -p 7000 --op SET -t 8 --dbsize 65536 --pool --replica-ops-percent 50

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