(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/pc/channel_manager_unittest.cc b/pc/channel_manager_unittest.cc
index ed09b72..999e36e 100644
--- a/pc/channel_manager_unittest.cc
+++ b/pc/channel_manager_unittest.cc
@@ -11,17 +11,17 @@
 #include <memory>
 
 #include "absl/memory/memory.h"
-#include "api/rtcerror.h"
+#include "api/rtc_error.h"
 #include "api/test/fake_media_transport.h"
-#include "media/base/fakemediaengine.h"
-#include "media/base/testutils.h"
-#include "media/engine/fakewebrtccall.h"
-#include "p2p/base/dtlstransportinternal.h"
-#include "p2p/base/fakedtlstransport.h"
-#include "p2p/base/p2pconstants.h"
-#include "p2p/base/packettransportinternal.h"
-#include "pc/channelmanager.h"
-#include "pc/dtlssrtptransport.h"
+#include "media/base/fake_media_engine.h"
+#include "media/base/test_utils.h"
+#include "media/engine/fake_webrtc_call.h"
+#include "p2p/base/dtls_transport_internal.h"
+#include "p2p/base/fake_dtls_transport.h"
+#include "p2p/base/p2p_constants.h"
+#include "p2p/base/packet_transport_internal.h"
+#include "pc/channel_manager.h"
+#include "pc/dtls_srtp_transport.h"
 #include "rtc_base/checks.h"
 #include "rtc_base/thread.h"
 #include "test/gtest.h"