(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/logging/rtc_event_log/encoder/var_int.h b/logging/rtc_event_log/encoder/var_int.h
index 86bc7ca..390ac90 100644
--- a/logging/rtc_event_log/encoder/var_int.h
+++ b/logging/rtc_event_log/encoder/var_int.h
@@ -8,15 +8,15 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#ifndef LOGGING_RTC_EVENT_LOG_ENCODER_VARINT_H_
-#define LOGGING_RTC_EVENT_LOG_ENCODER_VARINT_H_
+#ifndef LOGGING_RTC_EVENT_LOG_ENCODER_VAR_INT_H_
+#define LOGGING_RTC_EVENT_LOG_ENCODER_VAR_INT_H_
 
 #include <stddef.h>
 #include <stdint.h>
 #include <string>
 
 #include "absl/strings/string_view.h"
-#include "rtc_base/bitbuffer.h"
+#include "rtc_base/bit_buffer.h"
 
 namespace webrtc {
 
@@ -44,4 +44,4 @@
 
 }  // namespace webrtc
 
-#endif  // LOGGING_RTC_EVENT_LOG_ENCODER_VARINT_H_
+#endif  // LOGGING_RTC_EVENT_LOG_ENCODER_VAR_INT_H_