(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}

examples/unityplugin/class_reference_holder.h

@@ -13,8 +13,8 @@
 // specific java class into JNI c++ side, so that our c++ code can
 // call those java functions.
 
-#ifndef EXAMPLES_UNITYPLUGIN_CLASSREFERENCEHOLDER_H_
-#define EXAMPLES_UNITYPLUGIN_CLASSREFERENCEHOLDER_H_
+#ifndef EXAMPLES_UNITYPLUGIN_CLASS_REFERENCE_HOLDER_H_
+#define EXAMPLES_UNITYPLUGIN_CLASS_REFERENCE_HOLDER_H_
 
 #include <jni.h>
 #include <map>
@@ -34,4 +34,4 @@ jclass FindClass(JNIEnv* jni, const char* name);
 
 }  // namespace unity_plugin
 
-#endif  // EXAMPLES_UNITYPLUGIN_CLASSREFERENCEHOLDER_H_
+#endif  // EXAMPLES_UNITYPLUGIN_CLASS_REFERENCE_HOLDER_H_