fix: DualVMToken totalSupply (#1569)

Fixes an issue where `totalSupply` was skipping the high-part of the
u256 reported in
code-423n4/2024-09-kakarot-findings#15

- Correctly deserialize return value
- Update test to launch a token with populated (low, high) parts of the
u256 struct

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Co-authored-by: Clément Walter <clement0walter@gmail.com>

solidity_contracts/src/CairoPrecompiles/DualVmToken.sol

@@ -79,7 +79,8 @@ contract DualVmToken {
 
     function totalSupply() external view returns (uint256) {
         bytes memory returnData = starknetToken.staticcallCairo("total_supply");
-        return abi.decode(returnData, (uint256));
+        (uint128 valueLow, uint128 valueHigh) = abi.decode(returnData, (uint128, uint128));
+        return uint256(valueLow) + (uint256(valueHigh) << 128);
     }
 
     /// @dev This function is used to get the balance of an evm account

tests/end_to_end/CairoPrecompiles/test_dual_vm_token.py

@@ -12,7 +12,7 @@
 @pytest_asyncio.fixture(scope="function")
 async def starknet_token(owner):
     address = await deploy_starknet(
-        "StarknetToken", int(1e18), owner.starknet_contract.address
+        "StarknetToken", int(2**256 - 1), owner.starknet_contract.address
     )
     return get_contract_starknet("StarknetToken", address=address)