(4) Rename files to snake_case: update BUILD.gn, include paths, header guards, and DEPS entries

Mechanically generated by running this command:

tools_webrtc/do-renames.sh update all-renames.txt && git cl format

Then manually updating:

tools_webrtc/sanitizers/tsan_suppressions_webrtc.cc

Bug: webrtc:10159
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I54824cd91dada8fc3ee3d098f971bc319d477833
Reviewed-on: https://webrtc-review.googlesource.com/c/115653
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26226}

rtc_base/network_route.h

@@ -8,8 +8,8 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#ifndef RTC_BASE_NETWORKROUTE_H_
-#define RTC_BASE_NETWORKROUTE_H_
+#ifndef RTC_BASE_NETWORK_ROUTE_H_
+#define RTC_BASE_NETWORK_ROUTE_H_
 
 #include <stdint.h>
 
@@ -30,4 +30,4 @@ struct NetworkRoute {
 };
 }  // namespace rtc
 
-#endif  // RTC_BASE_NETWORKROUTE_H_
+#endif  // RTC_BASE_NETWORK_ROUTE_H_