feat: Add swap method with tests

Changes:
- If the tokenIn is ETH, skip permit2 approval
- Make executors payable: When using delegatecall the executor inherits the execution context of whoever calls it. Our main swap function can accept ETH, it needs to be payable so by consequence the executors also need to be.
- Set uniswap v2 executor in test router
- Add tests for all possible cases of swap
- Add tests for all cases of splitSwap
- Add test functions to handle permit2 and encode swaps

--- don't change below this line ---
ENG-4041 Took 3 hours 50 minutes

Took 49 seconds


Took 14 seconds

foundry/interfaces/IExecutor.sol

@@ -22,6 +22,7 @@ interface IExecutor {
      */
     function swap(uint256 givenAmount, bytes calldata data)
         external
+        payable
         returns (uint256 calculatedAmount);
 }