* op-node: log mgasps across block processing lifecycle

* op-node: add 'import_time' field to block processing log

* op-node: make log message more descriptive

* op-node: log legacy codepath for InsertUnsafePayload

* op-node: include final ForkchoiceUpdate in block insertion time

* op-node: remove unused BuildTime field from events

* op-node: encapsulate log logic in TryUpdateEngineEvent methods

* op-node: linter fix

* op-node: add comment and adjust sync log wording

* op-node: fix BlockHash, BlockNumber in log

* op-node: seq add BuildStarted to PayloadProcessEvent

* op-node: refactor getBlockProcessingMetrics, protect against divide-by-zero