(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/api/media_constraints_interface.h b/api/media_constraints_interface.h
index c9a6e1b..fc49cbe 100644
--- a/api/media_constraints_interface.h
+++ b/api/media_constraints_interface.h
@@ -18,15 +18,15 @@
 // be removed from WebRTC.
 // https://bugs.chromium.org/p/webrtc/issues/detail?id=9239
 
-#ifndef API_MEDIACONSTRAINTSINTERFACE_H_
-#define API_MEDIACONSTRAINTSINTERFACE_H_
+#ifndef API_MEDIA_CONSTRAINTS_INTERFACE_H_
+#define API_MEDIA_CONSTRAINTS_INTERFACE_H_
 
 #include <stddef.h>
 #include <string>
 #include <vector>
 
 #include "api/audio_options.h"
-#include "api/peerconnectioninterface.h"
+#include "api/peer_connection_interface.h"
 
 namespace webrtc {
 
@@ -156,4 +156,4 @@
 
 }  // namespace webrtc
 
-#endif  // API_MEDIACONSTRAINTSINTERFACE_H_
+#endif  // API_MEDIA_CONSTRAINTS_INTERFACE_H_