Reduce noise in Debug impl of RuntimeVariableList (#8007)

The default debug output of these types contains a lot of unnecessary noise making it hard to read.

This PR removes the type and extra fields from debug output to make logs easier to read.

`len` could be potentially useful in some cases, but this gives us flexibility to only log it separately if we need it.

Related PR in `ssz_types`:
- https://github.com/sigp/ssz_types/pull/57


  


Co-Authored-By: Jimmy Chen <jchen.tc@gmail.com>

consensus/types/src/runtime_fixed_vector.rs

@@ -2,12 +2,21 @@
 //!
 //! The length of the list cannot be changed once it is set.
 
-#[derive(Clone, Debug)]
+use std::fmt;
+use std::fmt::Debug;
+
+#[derive(Clone)]
 pub struct RuntimeFixedVector<T> {
     vec: Vec<T>,
     len: usize,
 }
 
+impl<T: Debug> Debug for RuntimeFixedVector<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:?} (len={})", self.vec, self.len)
+    }
+}
+
 impl<T: Clone + Default> RuntimeFixedVector<T> {
     pub fn new(vec: Vec<T>) -> Self {
         let len = vec.len();

consensus/types/src/runtime_var_list.rs

@@ -4,6 +4,8 @@ use serde::de::Error as DeError;
 use serde::{Deserialize, Deserializer, Serialize};
 use ssz::Decode;
 use ssz_types::Error;
+use std::fmt;
+use std::fmt::Debug;
 use std::ops::{Deref, Index, IndexMut};
 use std::slice::SliceIndex;
 use tree_hash::{Hash256, MerkleHasher, PackedEncoding, TreeHash, TreeHashType};
@@ -42,7 +44,7 @@ use tree_hash::{Hash256, MerkleHasher, PackedEncoding, TreeHash, TreeHashType};
 /// assert!(long.push(6).is_err());
 ///
 /// ```
-#[derive(Debug, Clone, Serialize, Deserialize, Derivative)]
+#[derive(Clone, Serialize, Deserialize, Derivative)]
 #[derivative(PartialEq, Eq, Hash(bound = "T: std::hash::Hash"))]
 #[serde(transparent)]
 pub struct RuntimeVariableList<T> {
@@ -51,6 +53,12 @@ pub struct RuntimeVariableList<T> {
     max_len: usize,
 }
 
+impl<T: Debug> Debug for RuntimeVariableList<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:?} (max_len={})", self.vec, self.max_len)
+    }
+}
+
 impl<T> RuntimeVariableList<T> {
     /// Returns `Ok` if the given `vec` equals the fixed length of `Self`. Otherwise returns
     /// `Err(OutOfBounds { .. })`.