Implement Gloas withdrawals and refactor (#8692)

Co-Authored-By: Michael Sproul <michael@sigmaprime.io>

Co-Authored-By: Michael Sproul <michaelsproul@users.noreply.github.com>

consensus/state_processing/src/per_block_processing/errors.rs

@@ -90,6 +90,14 @@ pub enum BlockProcessingError {
         found: Hash256,
     },
     WithdrawalCredentialsInvalid,
+    /// This should be unreachable unless there's a logical flaw in the spec for withdrawals.
+    WithdrawalsLimitExceeded {
+        limit: usize,
+        prior_withdrawals: usize,
+    },
+    /// Unreachable unless there's a logic error in LH.
+    IncorrectExpectedWithdrawalsVariant,
+    MissingLastWithdrawal,
     PendingAttestationInElectra,
 }