DoubleSigningSlasher Foundry test (#10839)

* fixed gold token actors

* ++ doubleSigningSlasher test

* ∆ conflicting function name

* set epochSize manually

packages/protocol/contracts/governance/test/MockUsingPrecompiles.sol

@@ -1,7 +1,5 @@
 pragma solidity ^0.5.13;
 
-import "../DoubleSigningSlasher.sol";
-
 contract MockUsingPrecompiles {
  mapping(bytes32 => bytes32) verifiedSealBitmap;
  mapping(uint256 => bytes32) parentSealBitmap;
@@ -27,6 +25,7 @@ contract MockUsingPrecompiles {
 
  function calcEpoch(uint256 blockNumber) internal pure returns (uint256) {
  uint256 epochSize = 100;
+
  // Follows GetEpochNumber from celo-blockchain/blob/master/consensus/istanbul/utils.go
  uint256 epochNumber = blockNumber / epochSize;
  if (blockNumber % epochSize == 0) {

packages/protocol/test-sol/common/GoldToken.t.sol

@@ -17,7 +17,7 @@ contract GoldTokenTest is Test {
  function setUp() public {
  goldToken = new GoldToken(true);
  receiver = actor("receiver");
- receiver = actor("sender");
+ sender = actor("sender");
  vm.deal(receiver, ONE_GOLDTOKEN);
  vm.deal(sender, ONE_GOLDTOKEN);
  }