perf: use picoev as default Server for improve response concurrency

tests/test_picoev_benchmark.v

@@ -0,0 +1,68 @@
+// Keep-Alive HTTP 基准测试
+module main
+
+import net
+import time
+
+fn main() {
+	addr := '127.0.0.1:9999'
+	requests := 10000
+	
+	println('=== Keep-Alive HTTP 基准测试 ===')
+	println('目标: ${addr}')
+	println('请求数: ${requests}')
+	println('')
+	
+	// 建立连接
+	mut conn := net.dial_tcp(addr) or {
+		println('连接失败: ${err}')
+		return
+	}
+	defer { conn.close() or {} }
+	
+	// 预热
+	println('预热中...')
+	for _ in 0 .. 100 {
+		send_keepalive_request(mut conn, addr) or {
+			// 重连
+			conn = net.dial_tcp(addr) or { continue }
+			continue
+		}
+	}
+	
+	// 正式测试
+	println('开始测试...')
+	sw := time.new_stopwatch()
+	mut success := 0
+	
+	for _ in 0 .. requests {
+		send_keepalive_request(mut conn, addr) or {
+			// 重连
+			conn = net.dial_tcp(addr) or { continue }
+			continue
+		}
+		success++
+	}
+	
+	elapsed := sw.elapsed()
+	elapsed_ms := f64(elapsed.milliseconds())
+	rps := f64(success) * 1000.0 / elapsed_ms
+	avg_us := elapsed_ms * 1000.0 / f64(success)
+	
+	println('')
+	println('=== 结果 ===')
+	println('成功请求: ${success}/${requests}')
+	println('总耗时: ${elapsed_ms:.0f}ms')
+	println('吞吐量: ${rps:.0f} req/s')
+	println('平均延迟: ${avg_us:.2f}μs')
+}
+
+fn send_keepalive_request(mut conn net.TcpConn, addr string) ! {
+	// 发送 HTTP 请求 (Keep-Alive)
+	request := 'GET /api/health HTTP/1.1\r\nHost: ${addr}\r\nConnection: keep-alive\r\n\r\n'
+	conn.write_string(request)!
+	
+	// 读取响应头和体
+	mut buf := []u8{len: 256}
+	conn.read(mut buf) or {}
+}