Replace "coin" with "network"

The Processor's coins folder referred to the networks it could process, as did
its Coin trait. This, and other similar cases throughout the codebase, have now
been corrected.

Also corrects dated documentation for a key pair is confirmed under the
validator-sets pallet.

coordinator/src/main.rs

@@ -398,7 +398,7 @@ pub async fn handle_processors<D: Db, Pro: Processors, P: P2p>(
         key_gen::ProcessorMessage::Shares { id, shares } => {
           Some(Transaction::DkgShares(id.attempt, shares, Transaction::empty_signed()))
         }
-        key_gen::ProcessorMessage::GeneratedKeyPair { id, substrate_key, coin_key } => {
+        key_gen::ProcessorMessage::GeneratedKeyPair { id, substrate_key, network_key } => {
           assert_eq!(
             id.set.network, msg.network,
             "processor claimed to be a different network than it was for GeneratedKeyPair",
@@ -411,7 +411,7 @@ pub async fn handle_processors<D: Db, Pro: Processors, P: P2p>(
             id.set.network,
             (
               Public(substrate_key),
-              coin_key
+              network_key
                 .try_into()
                 .expect("external key from processor exceeded max external key length"),
             ),