(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/pc/rtp_parameters_conversion_unittest.cc b/pc/rtp_parameters_conversion_unittest.cc
index f4f1b92..27708cc 100644
--- a/pc/rtp_parameters_conversion_unittest.cc
+++ b/pc/rtp_parameters_conversion_unittest.cc
@@ -10,7 +10,7 @@
 
 #include <algorithm>
 
-#include "pc/rtpparametersconversion.h"
+#include "pc/rtp_parameters_conversion.h"
 #include "rtc_base/gunit.h"
 
 namespace webrtc {