Previously, UnitTestTimer paused for 1 second each time it wanted to
test that the timer did (or didn't) record the time elapsing. This was
done 3 times per test and tested seperately on (currently) 5 devices.
The accumulated 15 seconds is not a whole lot, but it can add up when
coupled with the well over 300 other tests.

This change moves from the POSIX sleep function (which is limited to
increments of 1 second) to the updated C++ thread/chrono classes. The
amount of time to wait each time is now 0.25 seconds, which should speed
the test up by 4 times. The risk is that the shorter wait times can
throw off the results if the computer being run on is busy. If that is
the case, we can bump up the wait time (perhaps to 0.5 seconds).