Cleanup consensus/types re-exports (#8643)

Removes some of the temporary re-exports in `consensus/types`.

I am doing this in multiple parts to keep each diff small.


Co-Authored-By: Mac L <mjladson@pm.me>

beacon_node/beacon_chain/src/observed_attesters.rs

@@ -20,7 +20,7 @@ use std::collections::{HashMap, HashSet};
 use std::hash::Hash;
 use std::marker::PhantomData;
 use typenum::Unsigned;
-use types::slot_data::SlotData;
+use types::SlotData;
 use types::{Epoch, EthSpec, Hash256, Slot};
 
 /// The maximum capacity of the `AutoPruningEpochContainer`.