Various test cases where legacy keys exist and are used to migrate to
dnssec-policy. These once existed as shell script but were removed
because auto-dnssec was removed. But the test cases are still useful
if one wants to migrate to dnssec-policy with such legacy keys.
The tests were previously removed in commit
906dd57b68 as part of MR !8085.
(cherry picked from commit 6499814835)
