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

common/validator_dir/src/builder.rs

@@ -214,6 +214,7 @@ impl<'a> Builder<'a> {
                         .write(true)
                         .read(true)
                         .create(true)
+                        .truncate(true)
                         .open(path)
                         .map_err(Error::UnableToSaveDepositData)?
                         .write_all(hex.as_bytes())
@@ -231,6 +232,7 @@ impl<'a> Builder<'a> {
                         .write(true)
                         .read(true)
                         .create(true)
+                        .truncate(true)
                         .open(path)
                         .map_err(Error::UnableToSaveDepositAmount)?
                         .write_all(format!("{}", amount).as_bytes())