dnssec-ksr keygen -o to create KSKs

dnssec-ksr keygen -o to create KSKs

Add an option to dnssec-ksr keygen, -o, to create KSKs instead of ZSKs.
This way, we can create a set of KSKS for a given period too.

For KSKs we also need to set timing metadata, including "SyncPublish"
and "SyncDelete". This functionality already exists in keymgr.c so
let's make the function accessible.

Replace dnssec-keygen calls with dnssec-ksr keygen for KSK in the
ksr system test and check keys for created KSKs as well. This requires
a slight modification of the check_keys function to take into account
KSK timings and metadata.