Disallow genesis sync outside blob pruning window (#5038)

* Disallow Syncing From Genesis By Default

* Fix CLI Tests

* Perform checks in the `ClientBuilder`

* Tidy, fix tests

* Return an error based on the Deneb fork

* Fix typos

* Fix failing test

* Add missing CLI flag

* Fix CLI flags

* Add suggestion from Sean

* Fix conflict with blob sidecars epochs

---------

Co-authored-by: Mark Mackey <mark@sigmaprime.io>

lighthouse/tests/beacon_node.rs

@@ -92,6 +92,22 @@ fn staking_flag() {
         });
 }
 
+#[test]
+fn allow_insecure_genesis_sync() {
+    CommandLineTest::new()
+        .run_with_zero_port()
+        .with_config(|config| {
+            assert_eq!(config.allow_insecure_genesis_sync, false);
+        });
+
+    CommandLineTest::new()
+        .flag("allow-insecure-genesis-sync", None)
+        .run_with_zero_port()
+        .with_config(|config| {
+            assert_eq!(config.allow_insecure_genesis_sync, true);
+        });
+}
+
 #[test]
 fn wss_checkpoint_flag() {
     let state = Some(Checkpoint {