Add missing includes checks.h/array_view.h

instead of relying on optional.h to included these 2 headers.

Bug: webrtc:9078
Change-Id: I7a4b3facd81690b8f107640487e129986c1f5ff6
Reviewed-on: https://webrtc-review.googlesource.com/68602
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22803}

rtc_tools/network_tester/config_reader.cc

@@ -12,6 +12,8 @@
 #include <string>
 #include <vector>
 
+#include "rtc_base/checks.h"
+
 namespace webrtc {
 
 ConfigReader::ConfigReader(const std::string& config_file_path)