key_vector_test: key vector testing parameters

Usage
-------
key_vector_test
   alt_dict_test_fail < disable | enable >,
   expht_test_fail < disable | enable >,
   fail_init       < disable | single | all >,
   test_assert     < disable | xl | h | hxl >,
   size_adjust     <ub4>,
   max_join_key_count <ub4>,
   force_merge_to_page < disable | enable >,
   assert_on_page  < disable | enable >,
   fail_plkg       < disable | enable >,
   assert_on_shared_dgkg_fail < disable | enable >,
   flatten         < default | liteminmax | efilter | noefilter | nohashefilter >,
   predicate       < default | liteminmax >,
   efilter         < default | insufficient | enough >,
   server_efilters < disable | enable >