Move rollover test cases to separate test dir

Move rollover test cases to separate test dir

In order to keep the kasp system test somewhat approachable, let's
move all rollover scenarios to its own test directory. Starting with
the manual rollover test cases.

A new test function is added to 'isctest.kasp', to verify that the
relationship metadata (Predecessor, Successor) is set correctly.

The configuration and setup for the zone 'manual-rollover.kasp' are
almost copied verbatim, the only exception is the keytimes. Similar
to the test kasp cases, we no longer set "SyncPublish/PublishCDS" in
the setup script. In addition to that, the offset is changed from one
day ago to one week ago, so that the key states match the timing
metadata (one day is too short to move a key from "hidden" to
"omnipresent").

(cherry picked from commit 4d08ec50d14deccb8d09eba8b56d7b7396144aac)