Convert kasp dnssectools tests to pytest

Convert kasp dnssectools tests to pytest

Convert the first couple of tests from 'kasp/tests.sh' to
'kasp/tests_kasp.py', those are test cases related to 'dnssec-keygen'
and 'dnssec-settime'.

For this, we also add a new KeyProperties method,
'policy_to_properties', that takes a list of strings which represent
the keys according to the dnssec-policy and the expected key states.