Work on testing the Router

Completes the `Executed` enum in the router. Adds an `Escape` struct. Both are
needed for testing purposes.

Documents the gas constants in intent and reasoning.

Adds modernized tests around key rotation and the escape hatch.

Also updates the rest of the codebase which had accumulated errors.

processor/ethereum/src/main.rs

@@ -6,11 +6,13 @@
 static ALLOCATOR: zalloc::ZeroizingAlloc<std::alloc::System> =
   zalloc::ZeroizingAlloc(std::alloc::System);
 
+use core::time::Duration;
 use std::sync::Arc;
 
+use alloy_core::primitives::U256;
 use alloy_simple_request_transport::SimpleRequest;
 use alloy_rpc_client::ClientBuilder;
-use alloy_provider::RootProvider;
+use alloy_provider::{Provider, RootProvider};
 
 use serai_client::validator_sets::primitives::Session;
 
@@ -62,10 +64,26 @@ async fn main() {
     ClientBuilder::default().transport(SimpleRequest::new(bin::url()), true),
   ));
 
+  let chain_id = {
+    let mut delay = Duration::from_secs(5);
+    loop {
+      match provider.get_chain_id().await {
+        Ok(chain_id) => break chain_id,
+        Err(e) => {
+          log::error!("failed to fetch the chain ID on boot: {e:?}");
+          tokio::time::sleep(delay).await;
+          delay = (delay + Duration::from_secs(5)).max(Duration::from_secs(120));
+        }
+      }
+    }
+  };
+
   bin::main_loop::<SetInitialKey, _, KeyGenParams, _>(
     db.clone(),
     Rpc { db: db.clone(), provider: provider.clone() },
-    Scheduler::<bin::Db>::new(SmartContract),
+    Scheduler::<bin::Db>::new(SmartContract {
+      chain_id: U256::from_le_slice(&chain_id.to_le_bytes()),
+    }),
     TransactionPublisher::new(db, provider, {
       let relayer_hostname = env::var("ETHEREUM_RELAYER_HOSTNAME")
         .expect("ethereum relayer hostname wasn't specified")