Move libctstiagent to test exports since it's for testing only. am: 3c51f78e0f am: 0a8f8e14f7 am: dc14b3d4f2

Original change: https://android-review.googlesource.com/c/platform/art/+/1703010

Change-Id: I66e9b0a8d15b50d08599ec08f0b8fd15d625679b