Eth1 network exit on wrong network id (#1563)

## Issue Addressed

Fixes #1509 

## Proposed Changes

Exit the beacon node if the eth1 endpoint points to an invalid eth1 network. Check the network id before every eth1 cache update and display an error log if the network id has changed to an invalid one.

testing/eth1_test_rig/src/ganache.rs

@@ -14,6 +14,8 @@ use web3::{
 /// How long we will wait for ganache to indicate that it is ready.
 const GANACHE_STARTUP_TIMEOUT_MILLIS: u64 = 10_000;
 
+const NETWORK_ID: u64 = 42;
+
 /// Provides a dedicated `ganachi-cli` instance with a connected `Web3` instance.
 ///
 /// Requires that `ganachi-cli` is installed and available on `PATH`.
@@ -42,6 +44,8 @@ impl GanacheInstance {
             .arg(format!("{}", port))
             .arg("--mnemonic")
             .arg("\"vast thought differ pull jewel broom cook wrist tribe word before omit\"")
+            .arg("--networkId")
+            .arg(format!("{}", NETWORK_ID))
             .spawn()
             .map_err(|e| {
                 format!(
@@ -97,6 +101,11 @@ impl GanacheInstance {
         endpoint(self.port)
     }
 
+    /// Returns the network id of the ganache instance
+    pub fn network_id(&self) -> u64 {
+        NETWORK_ID
+    }
+
     /// Increase the timestamp on future blocks by `increase_by` seconds.
     pub async fn increase_time(&self, increase_by: u64) -> Result<(), String> {
         self.web3