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

database_manager/src/lib.rs

@@ -356,6 +356,7 @@ pub fn inspect_db<E: EthSpec>(
 
                 let write_result = fs::OpenOptions::new()
                     .create(true)
+                    .truncate(true)
                     .write(true)
                     .open(&file_path)
                     .map_err(|e| format!("Failed to open file: {:?}", e))