Gloas modify process_withdrawals (#8281)

* add process withdrawals logic

* fix process_withdrawals test

* updates per consensus spec v1.6.0-beta.1 release

* add todo for is_parent_block_full

consensus/types/src/beacon_state.rs

@@ -2204,6 +2204,7 @@ impl<E: EthSpec> BeaconState<E> {
         }
     }
 
+    /// Return true if the parent block was full (both beacon block and execution payload were present).
     pub fn is_parent_block_full(&self) -> bool {
         match self {
             BeaconState::Base(_) | BeaconState::Altair(_) => false,