* Timer test - handle removal of Timer(ticker_data_t *)
* Timer test - use Chrono, don't test deprecated methods
* Kernel tick count test - TEST_ASSERT_WITHIN -> TEST_ASSERT_INT_WITHIN
* Mutex test - fix up Chrono changes
* SysTimer test - adapt to SysTimer Chrono changes
* Thread test - use Chrono
* SysTimer - devirtualize destructor
`SysTimer::set_wake_time` incorrectly assumed that the `SysTimer`s tick
count and the underlying HAL timer had the same zero base. This normally
holds, at least approximately, in RTOS builds where the HAL timer starts
from zero at the same time the SysTimer is initialised.
But in bare metal builds, the HAL timer could be started some time
before the SysTimer, giving a significant discrepancy.
Beyond that, there's no requirement for HAL timers to start from zero in
the spec.
Record the HAL timer start time to get the conversion right.