test: add comprehensive single-threaded comparison benchmarks

[hayabusa-cloud]

Summary

• Add uncontended benchmarks comparing atomix vs sync/atomic across all operation types
• Cover Load, Store, Add, Swap, CAS, CompareExchange, Or, And, Xor for Int32, Int64, Uintptr, and Uint128
• Each operation is benchmarked at every supported memory ordering (Relaxed, Acquire, Release, AcqRel)

Test plan

• make bench runs all benchmarks
• Benchmark names filter correctly: go test -bench=BenchmarkComp
• Zero allocations reported for all benchmarks (-benchmem)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[Copilot]

Pull request overview

Adds a new benchmark suite intended to provide comprehensive, single-threaded performance comparisons between sync/atomic and atomix across multiple operation types and memory orderings.

Changes:

• Introduces comprehensive_bench_test.go with a large set of uncontended benchmarks for Int32/Int64 operations (plus partial coverage for Uintptr and Uint128).
• Adds atomix-only benchmarks for operations not directly available in sync/atomic (e.g., CompareExchange, Xor).
• Adds barrier benchmarks for atomix memory fences.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.