Fix Rust beta compiler errors (1.77) (#5180)

* Lint fixes

* More fixes for beta compiler.

* Format fixes

* Move `#[allow(dead_code)]` to field level.

* Remove old comment.

* Update beacon_node/execution_layer/src/test_utils/mod.rs

Co-authored-by: João Oliveira <hello@jxs.pt>

* remove duplicate line

lighthouse/environment/src/lib.rs

@@ -434,7 +434,7 @@ impl<E: EthSpec> Environment<E> {
             async move { rx.next().await.ok_or("Internal shutdown channel exhausted") };
         futures::pin_mut!(inner_shutdown);
 
-        match self.runtime().block_on(async {
+        let register_handlers = async {
             let mut handles = vec![];
 
             // setup for handling SIGTERM
@@ -465,7 +465,9 @@ impl<E: EthSpec> Environment<E> {
             }
 
             future::select(inner_shutdown, future::select_all(handles.into_iter())).await
-        }) {
+        };
+
+        match self.runtime().block_on(register_handlers) {
             future::Either::Left((Ok(reason), _)) => {
                 info!(self.log, "Internal shutdown received"; "reason" => reason.message());
                 Ok(reason)