Find a way to attribute a failure during the finalization of KeyResharing protocol

[fjarri]

There is a point during finalization where we check if the resulting key assembles into the known verifying key. If there is an error there, we cannot attribute it to a specific party.

• Is there a way to do that? Perhaps by making a "correctness proof", similarly to how finalization errors are handled in CGGMP?
• Alternatively, if we decide we don't need that, a variant will have to be added to FinalizeError

[fjarri]

@Camialavi we will probably need an external expertise for that