Split iOS sdk in to separate targets

This CL splits the iOS sdk into separate static libraries for video,
audio, ui, common, and peerconnection-related code. This will in the
future make it easier to compile WebRTC without unneeded components.

BUG=webrtc:4867

Review-Url: https://codereview.webrtc.org/2862543002
Cr-Commit-Position: refs/heads/master@{#18166}

webrtc/sdk/objc/Framework/Classes/RTCTracing.mm

@@ -1,29 +0,0 @@
-/*
- *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-#import "WebRTC/RTCTracing.h"
-
-#include "webrtc/base/event_tracer.h"
-
-void RTCSetupInternalTracer() {
-  rtc::tracing::SetupInternalTracer();
-}
-
-BOOL RTCStartInternalCapture(NSString *filePath) {
-  return rtc::tracing::StartInternalCapture(filePath.UTF8String);
-}
-
-void RTCStopInternalCapture() {
-  rtc::tracing::StopInternalCapture();
-}
-
-void RTCShutdownInternalTracer() {
-  rtc::tracing::ShutdownInternalTracer();
-}