(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/sdk/objc/api/peerconnection/RTCRtpEncodingParameters+Private.h b/sdk/objc/api/peerconnection/RTCRtpEncodingParameters+Private.h
index fe60948..e3684d3 100644
--- a/sdk/objc/api/peerconnection/RTCRtpEncodingParameters+Private.h
+++ b/sdk/objc/api/peerconnection/RTCRtpEncodingParameters+Private.h
@@ -10,7 +10,7 @@
 
 #import "RTCRtpEncodingParameters.h"
 
-#include "api/rtpparameters.h"
+#include "api/rtp_parameters.h"
 
 NS_ASSUME_NONNULL_BEGIN