safe-tools: Add owner management methods to SafeTestLib

Can now easily add, remove and swap owners. Previous owner identification is
handled automatically if not specified. This allows for testing errors
by specifying an incorrect prevOwner.

packages/contracts-bedrock/test/safe-tools/SafeTestTools.sol

@@ -323,6 +323,40 @@ library SafeTestLib {
         return instance.safe.nonce();
     }
 
+    /// @dev Adds a new owner to the safe
+    function addOwnerWithThreshold(SafeInstance memory instance, address owner, uint256 threshold) internal {
+        execTransaction(
+            instance,
+            address(instance.safe),
+            0,
+            abi.encodeWithSelector(OwnerManager.addOwnerWithThreshold.selector, owner, threshold)
+        );
+    }
+
+    /// @dev Removes an owner from the safe. If not provided explictly, the identification of the prevOwner is handled
+    ///     automatically.
+    function removeOwner(SafeInstance memory instance, address prevOwner, address owner, uint256 threshold) internal {
+        prevOwner = prevOwner > address(0) ? prevOwner : SafeTestLib.getPrevOwner(owner, instance.owners);
+        execTransaction(
+            instance,
+            address(instance.safe),
+            0,
+            abi.encodeWithSelector(OwnerManager.removeOwner.selector, prevOwner, owner, threshold)
+        );
+    }
+
+    /// @dev Replaces an old owner with a new owner. If not provided explictly, the identification of the prevOwner is
+    /// handled automatically.
+    function swapOwner(SafeInstance memory instance, address prevOwner, address oldOwner, address newOwner) internal {
+        prevOwner = prevOwner > address(0) ? prevOwner : SafeTestLib.getPrevOwner(oldOwner, instance.owners);
+        execTransaction(
+            instance,
+            address(instance.safe),
+            0,
+            abi.encodeWithSelector(OwnerManager.swapOwner.selector, prevOwner, oldOwner, newOwner)
+        );
+    }
+
     /// @dev A wrapper for the full execTransaction method, if no signatures are provided it will
     ///         generate them for all owners.
     function execTransaction(