Batches with invalid contents should be flagged and skipped during aggregation

Currently if FireFly receives a batch with any malformed contents (such as a mismatched key due to #1175), it writes the batch to the database but none of the messages or data.
https://github.com/hyperledger/firefly/blob/057a7af8646426bc9d79a95b8d066838e3e6bc43/internal/events/persist_batch.go#L45

However, the saved batch has no marking to indicate that the contents were invalid. Therefore every time the aggregator rewinds to this batch, it will stall with "message not yet available".
https://github.com/hyperledger/firefly/blob/057a7af8646426bc9d79a95b8d066838e3e6bc43/internal/events/aggregator.go#L467

When batch contents are skipped in this fashion, FireFly should actually mark the batch somehow, and when the aggregator attempts to process a message from that batch, it should simply mark the pin dispatched and move on. This is different from rejecting the message, because the message will never even be inserted to the database - but there's no point in blocking the pin forever, since the message will never be valid.