net: add tcp_default_read_timeout and tcp_default_write_timeout and use them consistently

cmd/tools/vdoc.v

@@ -175,8 +175,6 @@ fn (mut cfg DocConfig) serve_html() {
 			server.close() or { }
 			panic(err)
 		}
-		conn.set_read_timeout(5 * time.second)
-		conn.set_write_timeout(5 * time.second)
 		handle_http_connection(mut conn, server_context)
 		conn.close() or { eprintln('error closing the connection: $err') }
 	}