test: timer: behavior: Enhancement for running this test

Zephyr timer is based on system ticks, there usually exists some time drift
due to round up/down errors between cycles, ticks and time delay, we
need to add those expected time drift into the bound calculation for
running this test.
Add a new config TIMER_TEST_PERIOD_MAX_DRIFT_PERCENT for users to set
expected maximum drift percentage for the timer period.

Signed-off-by: Chen Peng1 <peng1.chen@intel.com>