Move CtsSdkExtensions related files into their own directory. am: 8f5a58bbda am: 38c3eee4aa am: fe9f0642dc

Original change: https://android-review.googlesource.com/c/platform/packages/modules/SdkExtensions/+/1697065

Change-Id: Icfeddaf4c2f3be52f8eeb24cf728f54315b42bc4