In the new approach the host controls the device activity when the test
should start, finish and pass/fail status is send to device. Also deprecate
the test cases which can't accurately test.
The timing host tests reported success even if the total drift was
negative. This adds a check for this now.
The wait_us test now does not use a timer and just waits for 100000 us
between prints. This adds inherent drift, but it should still be well
under the limit.