Dedicated library for intending and evaluating cosigns

Not only cleans the existing cosign code but enables non-Serai-coordinators to
evaluate cosigns if they gain access to a feed of them (such as over an RPC).
This would let centralized services not only track the finalized chain yet the
cosigned chain without directly running a coordinator.

Still being wrapped up.

.github/workflows/msrv.yml

@@ -175,6 +175,7 @@ jobs:
         run: |
           cargo msrv verify --manifest-path coordinator/tributary/tendermint/Cargo.toml
           cargo msrv verify --manifest-path coordinator/tributary/Cargo.toml
+          cargo msrv verify --manifest-path coordinator/cosign/Cargo.toml
           cargo msrv verify --manifest-path coordinator/Cargo.toml
 
   msrv-substrate:

.github/workflows/tests.yml

@@ -61,6 +61,7 @@ jobs:
             -p serai-monero-processor \
             -p tendermint-machine \
             -p tributary-chain \
+            -p serai-cosign \
             -p serai-coordinator \
             -p serai-orchestrator \
             -p serai-docker-tests