Move ios_helpers to sdk folder

BUG=webrtc:5582

Review-Url: https://codereview.webrtc.org/2572743004
Cr-Original-Commit-Position: refs/heads/master@{#15649}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: beafee3009ac5f17e9e18d9452c3ae8d29ca92b0
6 files changed