feat(contracts/solve): native token support in middleman (#3023)

Noticed the `SolverNetMiddleman` contract couldn't transfer native
tokens, so I fixed that.

issue: none

contracts/solve/.gas-snapshot

@@ -36,4 +36,5 @@ SolverNet_Outbox_Fill_Test:test_fill_nativeExpense_succeeds() (gas: 253003)
 SolverNet_Outbox_Fill_Test:test_fill_native_overpayment_refund_succeeds() (gas: 285058)
 SolverNet_Outbox_Fill_Test:test_fill_no_fill_deadline_succeeds() (gas: 350052)
 SolverNet_Outbox_Fill_Test:test_fill_reverts() (gas: 406738)
-SolverNet_Outbox_Middleman_Test:test_executeAndTransfer_succeeds() (gas: 91348)
+SolverNet_Outbox_Middleman_Test:test_executeAndTransfer_erc20_succeeds() (gas: 91861)
+SolverNet_Outbox_Middleman_Test:test_executeAndTransfer_native_succeeds() (gas: 74450)

contracts/solve/src/SolverNetMiddleman.sol

@@ -16,7 +16,9 @@ contract SolverNetMiddleman is Initializable {
     function executeAndTransfer(address token, address to, address target, bytes calldata data) external payable {
         (bool success,) = target.call{ value: msg.value }(data);
         if (!success) revert CallFailed();
-        token.safeTransferAll(to);
+
+        if (token == address(0)) SafeTransferLib.safeTransferAllETH(to);
+        else token.safeTransferAll(to);
     }
 
     receive() external payable { }

contracts/solve/test/outbox/Middleman.t.sol

@@ -3,21 +3,31 @@ pragma solidity =0.8.24;
 
 import "../TestBase.sol";
 import { MockLST } from "test/utils/MockLST.sol";
+import { Refunder } from "test/utils/Refunder.sol";
 
 contract SolverNet_Outbox_Middleman_Test is TestBase {
     MockLST lst;
+    Refunder refunder;
 
     function setUp() public override {
         super.setUp();
         lst = new MockLST();
+        refunder = new Refunder();
     }
 
-    function test_executeAndTransfer_succeeds() public {
+    function test_executeAndTransfer_erc20_succeeds() public {
         vm.deal(solver, 1 ether);
         vm.prank(solver);
         middleman.executeAndTransfer{ value: 1 ether }(
             address(lst.token()), user, address(lst), abi.encodeWithSelector(MockLST.deposit.selector)
         );
-        assertEq(lst.token().balanceOf(user), 1 ether);
+        assertEq(lst.token().balanceOf(user), 1 ether, "user should have received 1 ether of the LST from middleman");
+    }
+
+    function test_executeAndTransfer_native_succeeds() public {
+        vm.deal(solver, 1 ether);
+        vm.prank(solver);
+        middleman.executeAndTransfer{ value: 1 ether }(address(0), user, address(refunder), "");
+        assertEq(user.balance, 1 ether, "user should have received 1 ether of native tokens from middleman");
     }
 }