Fix test_asyncio timeouts: don't measure the maximum duration, a test
should not measure a CI performance. Only measure the minimum
duration when a task has a timeout or delay. Add CLOCK_RES to
test_asyncio.utils.
Expect the test to be "short" but don't measure the exact performance
of the CI. SHORT_TIMEOUT is about 30 seconds whereas the cancelled
coroutine takes around 1 hour.