test: use b.Loop() to simplify the code and improve performance (#2704)

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## Overview

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B.Loop intentionally defeats compiler optimizations such as inlining so
that the benchmark is not entirely optimized away. Currently, however,
it may cause benchmarks to become slower in some cases due to increased
allocation; see https://go.dev/issue/73137.

Before this change:

```shell
go test -run=^$ -bench=. ./block/internal/syncing -timeout=1h
goos: darwin
goarch: arm64
pkg: github.com/evstack/ev-node/block/internal/syncing
cpu: Apple M1
BenchmarkSyncerIO/slow_producer-10         	      37	  27149786 ns/op
BenchmarkSyncerIO/slow_consumer-10         	      42	  27843880 ns/op
PASS
ok  	github.com/evstack/ev-node/block/internal/syncing	3.339s
```

After:

```shell
go test -run=^$ -bench=. ./block/internal/syncing -timeout=1h
goos: darwin
goarch: arm64
pkg: github.com/evstack/ev-node/block/internal/syncing
cpu: Apple M1
BenchmarkSyncerIO/slow_producer-10         	      40	  27021698 ns/op
BenchmarkSyncerIO/slow_consumer-10         	      42	  28333081 ns/op
PASS
ok  	github.com/evstack/ev-node/block/internal/syncing	3.070s
```

Signed-off-by: juejinyuxitu <juejinyuxitu@outlook.com>

Author: juejinyuxitu

block/internal/syncing/syncer_benchmark_test.go

@@ -38,8 +38,7 @@ func BenchmarkSyncerIO(b *testing.B) {
 	}
 	for name, spec := range cases {
 		b.Run(name, func(b *testing.B) {
-			b.ResetTimer()
-			for i := 0; i < b.N; i++ {
+			for b.Loop() {
 				fixt := newBenchFixture(b, spec.heights, spec.shuffledTx, spec.daDelay, spec.execDelay, true)
 
 				// run both loops