To prepare for the removal of software version from events, they must first be populated with empty values so that the hash of PCES events that still have version as part of their hash can still be calculated correctly when version is removed.

depends on #18377

This requires the Hedera application to compare the birth round of events to the last freeze round number to determine if the event's transactions should be handled or not. This requires storing the latest freeze round number in state. The value should be updated on startup, if the initial state is a freeze state. Importantly, this value must be updated (if needed) prior to handling any events.