Migrate utils to ethersjs v6 (#4736)

Co-authored-by: Hadrien Croubois <hadrien.croubois@gmail.com>
Co-authored-by: ernestognw <ernestognw@gmail.com>

contracts/mocks/MulticallHelper.sol

@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.20;
+
+import {ERC20MulticallMock} from "./token/ERC20MulticallMock.sol";
+
+contract MulticallHelper {
+    function checkReturnValues(
+        ERC20MulticallMock multicallToken,
+        address[] calldata recipients,
+        uint256[] calldata amounts
+    ) external {
+        bytes[] memory calls = new bytes[](recipients.length);
+        for (uint256 i = 0; i < recipients.length; i++) {
+            calls[i] = abi.encodeCall(multicallToken.transfer, (recipients[i], amounts[i]));
+        }
+
+        bytes[] memory results = multicallToken.multicall(calls);
+        for (uint256 i = 0; i < results.length; i++) {
+            require(abi.decode(results[i], (bool)));
+        }
+    }
+}