Move tests for com.android.internal.util out of coretests

These are very simple tests with no dependencies, and moving them
out of FrameworksCoreTests makes it possible to iterate much more
quickly.  "runtest frameworks-core" takes almost a minute just to
push to the device, before any tests even start running.

Bug: 25691379
Change-Id: I8d99316a5940e0171883b97c578f9a6882b699a0