(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}

system_wrappers/include/metrics.h

@@ -16,7 +16,7 @@
 #include <memory>
 #include <string>
 
-#include "rtc_base/atomicops.h"
+#include "rtc_base/atomic_ops.h"
 #include "rtc_base/checks.h"
 
 // Macros for allowing WebRTC clients (e.g. Chrome) to gather and aggregate

system_wrappers/source/clock.cc

@@ -17,7 +17,7 @@
 
 #include <mmsystem.h>
 
-#include "rtc_base/criticalsection.h"
+#include "rtc_base/critical_section.h"
 
 #elif defined(WEBRTC_POSIX)
 
@@ -27,7 +27,7 @@
 #endif  // defined(WEBRTC_POSIX)
 
 #include "rtc_base/synchronization/rw_lock_wrapper.h"
-#include "rtc_base/timeutils.h"
+#include "rtc_base/time_utils.h"
 
 namespace webrtc {
 

system_wrappers/source/metrics.cc

@@ -11,7 +11,7 @@
 
 #include <algorithm>
 
-#include "rtc_base/criticalsection.h"
+#include "rtc_base/critical_section.h"
 #include "rtc_base/thread_annotations.h"
 
 // Default implementation of histogram methods for WebRTC clients that do not