twister: pytest: use test timeout as the default base timeout

The default base timeout for pytest is statically set by
the TwisterHarnessConfig class to be 60 seconds. However,
sometimes it takes longer than 60s before the app starts
to run, especially on emulator/simulator where it takes
quite some time to start. So pass the test timeout as
the base timeout via pytest command line argument.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>