Add fluss-microbench module: YAML-driven performance testing framework

[platinumhamburg]

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Motivation

There is currently no standardized way to run reproducible performance tests against Fluss. This makes it difficult to detect regressions, compare optimizations, and establish baselines — especially for aggregation merge engine workloads (RBM32/64, LISTAGG, SUM, etc.).

Solution

Introduce a unified benchmarking module (fluss-microbench) that provides a CLI-driven performance testing framework for Fluss clusters.

Key Features:

• YAML-driven scenario configuration covering write, lookup, prefix-lookup, scan, and mixed workloads
• Dual-process architecture: Server (MiniCluster) runs in a forked JVM, Client runs in the main process, enabling independent resource sampling
• Five-layer metric collection: OS process (OSHI), JVM (MXBean), NMT, application-level (client + server metrics), and JFR
• Built-in presets: log-append, kv-upsert-get, kv-agg-mixed, kv-agg-listagg, kv-agg-rbm32, log-filter-pushdown
• Baseline management with --diff-previous and --diff-baseline for regression detection
• Structured JSON-lines stdout output, semantic exit codes, and --quick mode for fast iteration
• Dataset pre-generation for reproducible benchmarks
• HTML/CSV/JSON report generation with environment snapshots

CLI Commands:

• run, generate, validate, diff, baseline, list, clean

Anything else?

No response

Willingness to contribute

• I'm willing to submit a PR!