Cancel of operations in firefly

[RobertOttBS]

When we invoke a methods through firefly API on a evm smart contract and provide by accident a 'key' that is not known by the ethsigner, the firefly operation goes into a never-ending Pending state. On the evmconnect side, the operation can be deleted via the evmconnect API delete /transactions/ (as Matthiew helped me to do so). However, it does not change the status on Firefly core side from Pending to Failed.

It would be good to have a 'cancel' method for such stuck operations in the firefly core API or a way to set the status of such a transaction from 'Pending' to 'Failed'.

[awrichar]

Relates to #1255 (both deal with recovering from a transaction that has been submitted but cannot ever succeed).