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/RTCMediaConstraints+Private.h

@@ -1,54 +0,0 @@
-/*
- *  Copyright 2015 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/RTCMediaConstraints.h"
-
-#include <memory>
-
-#include "webrtc/api/mediaconstraintsinterface.h"
-
-namespace webrtc {
-
-class MediaConstraints : public MediaConstraintsInterface {
- public:
-  virtual ~MediaConstraints();
-  MediaConstraints();
-  MediaConstraints(
-      const MediaConstraintsInterface::Constraints& mandatory,
-      const MediaConstraintsInterface::Constraints& optional);
-  virtual const Constraints& GetMandatory() const;
-  virtual const Constraints& GetOptional() const;
-
- private:
-  MediaConstraintsInterface::Constraints mandatory_;
-  MediaConstraintsInterface::Constraints optional_;
-};
-
-}  // namespace webrtc
-
-
-NS_ASSUME_NONNULL_BEGIN
-
-@interface RTCMediaConstraints ()
-
-/**
- * A MediaConstraints representation of this RTCMediaConstraints object. This is
- * needed to pass to the underlying C++ APIs.
- */
-- (std::unique_ptr<webrtc::MediaConstraints>)nativeConstraints;
-
-/** Return a native Constraints object representing these constraints */
-+ (webrtc::MediaConstraintsInterface::Constraints)
-    nativeConstraintsForConstraints:
-        (NSDictionary<NSString *, NSString *> *)constraints;
-
-@end
-
-NS_ASSUME_NONNULL_END