Add adverserial tests

[spacebear21]

The official BIP78 test vector checks the happy path where both the sender and receiver act honestly. To catch and prevent bugs that may result in loss of funds, we should add tests that uphold the sender/receiver checklists for when one of the parties behaves maliciously, e.g. tries to steal funds from the other. One such test was added here but it would be great to cover more (all?) code paths in the checklists.

If we can come up with good test vectors for these, maybe consider adding them to the BIP.