feat: un-deprecate pendingWithdrawals mapping

src/contracts/core/DelegationManager.sol

@@ -458,7 +458,7 @@ contract DelegationManager is
         require(tokens.length == withdrawal.strategies.length, InputArrayLengthMismatch());
         require(msg.sender == withdrawal.withdrawer, WithdrawerNotCaller());
         bytes32 withdrawalRoot = calculateWithdrawalRoot(withdrawal);
-        require(_stakerQueuedWithdrawalRoots[withdrawal.staker].contains(withdrawalRoot), WithdrawalNotQueued());
+        require(pendingWithdrawals(withdrawalRoot), WithdrawalNotQueued());
 
         // TODO: is there a cleaner way to do this?
         uint32 completableTimestamp = getCompletableTimestamp(withdrawal.startTimestamp);
@@ -501,6 +501,9 @@ contract DelegationManager is
 
         delete queuedWithdrawals[withdrawalRoot];
 
+        // This storage is actively being deprecated, values are only being read or deleted.
+        delete _legacyPendingWithdrawals[withdrawalRoot];
+
         emit SlashingWithdrawalCompleted(withdrawalRoot);
     }
 
@@ -786,10 +789,13 @@ contract DelegationManager is
     }
 
     /// @inheritdoc IDelegationManager
-    function pendingWithdrawals(
-        bytes32 withdrawalRoot
-    ) public view returns (bool) {
-        return queuedWithdrawals[withdrawalRoot].staker != address(0);
+    function pendingWithdrawals(bytes32 withdrawalRoot) public view returns (bool) {
+        // Check if a non-legacy withdrawal is pending.
+        bool isWithdrawalPending = queuedWithdrawals[withdrawalRoot].staker != address(0);
+
+        // NOTE: We must also check legacy storage to ensure that 
+        // withdrawals queued before the slashing release are completable.
+        return isWithdrawalPending || _legacyPendingWithdrawals[withdrawalRoot];
     }
 
     /// @inheritdoc IDelegationManager

src/contracts/core/DelegationManagerStorage.sol

@@ -94,12 +94,13 @@ abstract contract DelegationManagerStorage is IDelegationManager {
 
     /// @notice Returns whether `delegationApprover` has already used the given `salt`.
     mapping(address delegationApprover => mapping(bytes32 salt => bool spent)) public delegationApproverSaltIsSpent;
-
+ 
     /// @dev Do not remove, deprecated storage.
     uint256 private __deprecated_minWithdrawalDelayBlocks;
 
-    /// @dev Do not remove, deprecated storage.
-    mapping(bytes32 withdrawalRoot => bool pending) private __deprecated_pendingWithdrawals;
+    /// @dev Returns whether a withdrawal is pending for a given `withdrawalRoot`.
+    /// @dev This variable is actively being deprecated, values should only be read or deleted.
+    mapping(bytes32 withdrawalRoot => bool pending) internal _legacyPendingWithdrawals;
 
     /// @notice Returns the total number of withdrawals that have been queued for a given `staker`.
     /// @dev This only increments (doesn't decrement), and is used to help ensure that otherwise identical withdrawals have unique hashes.