Use an enum for Coin/NetworkId

It originally wasn't an enum so software which had yet to update before an
integration wouldn't error (as now enums are strictly typed). The strict typing
is preferable though.

coordinator/src/substrate.rs

@@ -177,18 +177,7 @@ async fn handle_batch_and_burns<D: Db, Pro: Processor>(
 
   for burn in serai.get_burn_events(hash).await? {
     if let TokensEvent::Burn { address: _, balance, instruction } = burn {
-      // TODO: Move Network/Coin to an enum and provide this mapping
-      let network = {
-        use serai_client::primitives::*;
-        match balance.coin {
-          BITCOIN => BITCOIN_NET_ID,
-          ETHER => ETHEREUM_NET_ID,
-          DAI => ETHEREUM_NET_ID,
-          MONERO => MONERO_NET_ID,
-          invalid => panic!("burn from unrecognized coin: {invalid:?}"),
-        }
-      };
-
+      let network = balance.coin.network();
       network_had_event(&mut burns, network);
 
       // network_had_event should register an entry in burns