tests: kernel: timer: add test for starvation

Add a test that repeatedly reschedules a timer before it expires, and
has no other timers active.  If the timer internal state overflows due
to counter wrap either the uptime or the tick counter may appear to go
backwards.  The test runs until it fails, or until a specified amount
of measured time has passed.

This test is build-only for automated test programs as the default
limit to pass is one hour, and some platforms may require an even
longer period.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>