test(test-sol/integration): adds e2e test for GoldToken

This is a test run, to see how `setUp()` and contract definitions work.

1. run devchain

```sh
./migrations_sol/create_and_migrate_anvil_devchain.sh
```

2. run test against devchain

```sh
forge test \
--match-path test-sol/integration/Integration.t.sol \
--match-contract GoldTokenTest_General \
-vvv \
--fork-url http://127.0.0.1:8546
```

Tests pass

Output:

```sh
[⠰] Compiling...
No files changed, compilation skipped

Running 3 tests for test-sol/integration/Integration.t.sol:GoldTokenTest_General
[PASS] test_decimals() (gas: 10837)
Logs:
  GoldToken address is: 0xfE8CbC1cFA1b3b8256f310bdfd40E60597083448

[PASS] test_name() (gas: 12537)
Logs:
  GoldToken address is: 0xfE8CbC1cFA1b3b8256f310bdfd40E60597083448

[PASS] test_symbol() (gas: 12579)
Logs:
  GoldToken address is: 0xfE8CbC1cFA1b3b8256f310bdfd40E60597083448

Test result: ok. 3 passed; 0 failed; 0 skipped; finished in 135.40ms

Ran 1 test suites: 3 tests passed, 0 failed, 0 skipped (3 total tests)
```

packages/protocol/test-sol/integration/Integration.t.sol

@@ -3,17 +3,38 @@ pragma solidity ^0.5.13;
 
 import "celo-foundry/Test.sol";
 import "@celo-contracts/common/GoldToken.sol";
-// import "@celo-contracts/common/test/MockGoldToken.sol";
 import "forge-std/console.sol";
 import "@celo-contracts/common/interfaces/IRegistry.sol";
+import "@celo-contracts/common/GoldToken.sol";
+import "@celo-contracts/common/UsingRegistry.sol";
+import "openzeppelin-solidity/contracts/token/ERC20/IERC20.sol";
+import "forge-std/console2.sol";
 
-contract IntegrationTest is Test {
-  address constant registryAddress = address(0x000000000000000000000000000000000000ce10);
+contract IntegrationTest is Test, UsingRegistry {
   address account1 = actor("account1");
   address account2 = actor("account2");
+  address constant registryAddress = address(0x000000000000000000000000000000000000ce10);
   IRegistry registry = IRegistry(registryAddress);
+  GoldToken goldToken;
 
   function setUp() public {}
-
-  function test_dummy() public {}
 }
+
+contract GoldTokenTest_General is IntegrationTest  {
+  function setUp() public {
+    goldToken = GoldToken(registry.getAddressForStringOrDie("GoldToken"));
+    console2.log("GoldToken address is:", address(goldToken));
+  }
+
+  function test_name() public {
+    assertEq(goldToken.name(), "Celo native asset");
+  }
+
+  function test_symbol() public {
+    assertEq(goldToken.symbol(), "CELO");
+  }
+
+  function test_decimals() public {
+    assertEq(uint256(goldToken.decimals()), 18);
+  }
+}