* op-node: sequencer / engine events refactor

incl sequencer events fixes

* op-node: distinguish block sealing error kinds

* op-node: review fixes, stashed tweaks

* op-node: events based sequencer chaos test

* op-node: fix missing DerivedFrom data in attributes test

* op-node: drop old wip debugging work log

* op-node: sequencer move OnEvent function

* op-node: update stale todo comment

* op-node: detect derivation block-building as sequencer, and avoid conflict

* op-node: clarify comments and rename PayloadSealTemporaryErrorEvent to PayloadSealExpiredErrorEvent to describe applicability better

* op-node: prevent temporary engine error from influencing inactive sequencer