Add LoomProvider test for static calls

[enlight]

We've got tests for eth signed txs in https://github.com/loomnetwork/loom-js/blob/master/src/tests/e2e/client-test-tx-middleware.ts but we don't have any tests for static calls using foreign addresses.

Basically we need a version of the SimpleStore EVM contract that looks something like this:

contract SimpleStore {
  mapping(address => uint256) balances;

  function setBalance(uint256 _val) external {
    balances[msg.sender] = _val;
  }
  
  function getBalance() public view returns(uint256) {
    return balances[msg.sender];
  }
}

The test should then call setBalance followed by getBalance using the same caller (eth:0x...), and verify that the balance matches.

[eduardonunesp]

#311