1.57.0 lints (#2850)

## Issue Addressed

New rust lints

## Proposed Changes

- Boxing some enum variants
- removing some unused fields (is the validator lockfile unused? seemed so to me)

## Additional Info

- some error fields were marked as dead code but are logged out in areas
- left some dead fields in our ef test code because I assume they are useful for debugging?

Co-authored-by: realbigsean <seananderson33@gmail.com>

consensus/ssz/src/encode.rs

@@ -113,7 +113,7 @@ impl<'a> SszEncoder<'a> {
         F: Fn(&mut Vec<u8>),
     {
         if is_ssz_fixed_len {
-            ssz_append(&mut self.buf);
+            ssz_append(self.buf);
         } else {
             self.buf
                 .extend_from_slice(&encode_length(self.offset + self.variable_bytes.len()));
@@ -129,7 +129,7 @@ impl<'a> SszEncoder<'a> {
     pub fn finalize(&mut self) -> &mut Vec<u8> {
         self.buf.append(&mut self.variable_bytes);
 
-        &mut self.buf
+        self.buf
     }
 }