fix(arbitration): fix ETH transfer in KlerosCore and dispute-kits and add SafeSend.sol in library

Author: hurstelm

contracts/src/arbitration/KlerosCoreBase.sol

@@ -90,7 +90,6 @@ abstract contract KlerosCoreBase is IArbitratorV2, Initializable, UUPSProxiable
 
     uint256 private constant ALPHA_DIVISOR = 1e4; // The number to divide `Court.alpha` by.
     uint256 private constant NON_PAYABLE_AMOUNT = (2 ** 256 - 2) / 2; // An amount higher than the supply of ETH.
-    address constant WETH_ADDRESS = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2; // The address of Ethereum Mainnet for WETH send
 
     address public governor; // The governor of the contract.
     address public guardian; // The guardian able to pause asset withdrawals.

contracts/src/arbitration/dispute-kits/DisputeKitClassicBase.sol

@@ -14,6 +14,7 @@ import {WethLike, SafeSend} from "../../libraries/SafeSend.sol";
 /// - an incentive system: equal split between coherent votes,
 /// - an appeal system: fund 2 choices only, vote on any choice.
 abstract contract DisputeKitClassicBase is IDisputeKit, Initializable, UUPSProxiable {
+    using SafeSend for address payable;
     // ************************************* //
     // *             Structs               * //
     // ************************************* //