(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}

sdk/android/native_unittests/codecs/wrapper_unittest.cc

@@ -9,7 +9,7 @@
  */
 
 #include "sdk/android/native_api/codecs/wrapper.h"
-#include "media/base/mediaconstants.h"
+#include "media/base/media_constants.h"
 #include "sdk/android/generated_native_unittests_jni/jni/CodecsWrapperTestHelper_jni.h"
 #include "test/gtest.h"