Move ContentSuggestions identifiers to custom target

ios/chrome/browser/ui/content_suggestions/content_suggestion_identifier.mm

-// Copyright 2017 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#import "ios/chrome/browser/ui/content_suggestions/content_suggestion_identifier.h"
-
-#include "base/mac/foundation_util.h"
-
-#if !defined(__has_feature) || !__has_feature(objc_arc)
-#error "This file requires ARC support."
-#endif
-
-@implementation ContentSuggestionIdentifier
-
-@synthesize sectionInfo = _sectionInfo;
-@synthesize IDInSection = _IDInSection;
-
-#pragma mark - NSObject
-
-- (BOOL)isEqual:(id)object {
-  if (self == object) {
-    return YES;
-  }
-
-  if (![object isKindOfClass:[ContentSuggestionIdentifier class]]) {
-    return NO;
-  }
-
-  ContentSuggestionIdentifier* other =
-      base::mac::ObjCCastStrict<ContentSuggestionIdentifier>(object);
-
-  return self.sectionInfo == other.sectionInfo &&
-         self.IDInSection == other.IDInSection;
-}
-
-@end