Extract and log transaction failure reason

[matthiasgeihs]

The operator tracks the status of challenge response transactions and logs an error if a transaction fails. Currently we do not log the failure reason because it is unclear how failure information can be extracted from go-ethereum.

Ideally we would like to log an error with the error reason (e.g., "out of gas") if a challenge response transaction fails.

[sebastianst]

Not sure if this will also cover "out of gas", but #54 should cover other revert reasons.

[ggwpez]

Not sure if this will also cover "out of gas", but #54 should cover other revert reasons.

In most cases it should detect an "out of gas" error but since ethereum has no canonical way of detecting this, there are some cases where it will return with a generic reason.

#62 addresses this, i will link it in #54.