(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}
diff --git a/rtc_base/signal_thread_unittest.cc b/rtc_base/signal_thread_unittest.cc
index eeae030..2bc0dda 100644
--- a/rtc_base/signal_thread_unittest.cc
+++ b/rtc_base/signal_thread_unittest.cc
@@ -10,10 +10,10 @@
 
 #include <memory>
 
-#include "rtc_base/constructormagic.h"
+#include "rtc_base/constructor_magic.h"
 #include "rtc_base/gunit.h"
-#include "rtc_base/signalthread.h"
-#include "rtc_base/socketserver.h"
+#include "rtc_base/signal_thread.h"
+#include "rtc_base/socket_server.h"
 #include "rtc_base/thread.h"
 #include "test/gtest.h"