Two more kasp test cases converted to pytest

Two more kasp test cases converted to pytest

The zone 'pregenerated.kasp' is a case where there already exist more
keys than required. For this we set the 'pregenerated' setting. This
will change the 'keydir_to_keylist' function behavior: Only keys in use
are considered. A key is in use if all of the states are either
undefined, or set to 'hidden'.

The 'some-keys.kasp' zone is similar to 'pregenerated.kasp', except
only some keys have been pregenerated.

(cherry picked from commit 43ded45ae9af1b5ad93a68444ac289574ae703a2)