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

processor/src/multisigs/mod.rs

@@ -938,7 +938,8 @@ impl<D: Db, N: Network> MultisigManager<D, N> {
         }
 
         // Save the plans created while scanning
-        // TODO: Should we combine all of these plans?
+        // TODO: Should we combine all of these plans to reduce the fees incurred from their
+        // execution? They're refunds and forwards. Neither should need isolate Plan/Eventualities.
         MultisigsDb::<N, D>::set_plans_from_scanning(txn, block_number, plans);
 
         // If any outputs were delayed, append them into this block