(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.cc b/api/media_constraints_interface.cc
index b66ba05..ddf5559 100644
--- a/api/media_constraints_interface.cc
+++ b/api/media_constraints_interface.cc
@@ -8,12 +8,12 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
-#include "api/mediaconstraintsinterface.h"
+#include "api/media_constraints_interface.h"
 
 #include "absl/types/optional.h"
-#include "api/peerconnectioninterface.h"
-#include "media/base/mediaconfig.h"
-#include "rtc_base/stringencode.h"
+#include "api/peer_connection_interface.h"
+#include "media/base/media_config.h"
+#include "rtc_base/string_encode.h"
 
 namespace {