Nyzo 634: unconfirmed-state improvements

Nyzo version 634 (commit on GitHub) improves management of unconfirmed-state processing.

This version affects the client.

In ClientDataManager, the previousFrozen EdgeHeight is stored outside the primary loop. This allows detection of frozen-edge changes, and processes that only need to be performed once per block are no longer called every loop iteration.

The NyzoScriptManager.processBlock() method is now only called once per block. The TransactionForwardCommand.performMaintenance() method is also now called once per block. This method was previously run periodically by the TransactionForwardCommand when it received transactions to prevent the recentlyForwardedTransactions map from growing too large. The ClientDataManager has a different motivation for running the method: to clear out older transactions so they do not get picked up by the NyzoScript Manager.

In TransactionForwardCommand, reset of the requestsSinceMaintenance counter was moved inside the performMaintenance() method so reset will always occur when maintenance is performed.

In NyzoScriptManager, filtering was added to ensure that all transactions that no longer have an opportunity to be incorporated into a confirmed script state are removed before processing of the unconfirmed state.