(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/video/end_to_end_tests/codec_tests.cc b/video/end_to_end_tests/codec_tests.cc
index f446228..3c9b39c 100644
--- a/video/end_to_end_tests/codec_tests.cc
+++ b/video/end_to_end_tests/codec_tests.cc
@@ -14,8 +14,8 @@
 #include "api/video/color_space.h"
 #include "api/video/video_rotation.h"
 #include "common_video/test/utilities.h"
-#include "media/engine/internaldecoderfactory.h"
-#include "media/engine/internalencoderfactory.h"
+#include "media/engine/internal_decoder_factory.h"
+#include "media/engine/internal_encoder_factory.h"
 #include "modules/video_coding/codecs/h264/include/h264.h"
 #include "modules/video_coding/codecs/multiplex/include/multiplex_decoder_adapter.h"
 #include "modules/video_coding/codecs/multiplex/include/multiplex_encoder_adapter.h"