Route blame between Processor and Coordinator (#427)

* Have processor report errors during the DKG to the coordinator

* Add RemoveParticipant, InvalidDkgShare to coordinator

* Route DKG blame around coordinator

* Allow public construction of AdditionalBlameMachine

Necessary for upcoming work on handling DKG blame in the processor and
coordinator.

Additionally fixes a publicly reachable panic when commitments parsed with one
ThresholdParams are used in a machine using another set of ThresholdParams.

Renames InvalidProofOfKnowledge to InvalidCommitments.

* Remove unused error from dleq

* Implement support for VerifyBlame in the processor

* Have coordinator send the processor share message relevant to Blame

* Remove desync between processors reporting InvalidShare and ones reporting GeneratedKeyPair

* Route blame on sign between processor and coordinator

Doesn't yet act on it in coordinator.

* Move txn usage as needed for stable Rust to build

* Correct InvalidDkgShare serialization

crypto/dleq/src/cross_group/mod.rs

@@ -95,9 +95,6 @@ impl<G: PrimeGroup> Generators<G> {
 /// Error for cross-group DLEq proofs.
 #[derive(Error, PartialEq, Eq, Debug)]
 pub enum DLEqError {
-  /// Invalid proof of knowledge.
-  #[error("invalid proof of knowledge")]
-  InvalidProofOfKnowledge,
   /// Invalid proof length.
   #[error("invalid proof length")]
   InvalidProofLength,