Call fallback function in transfer actions

[CoderZhi]

https://github.com/iotexproject/iotex-core/blob/7c758ab75007a17606563303816229b3d252778f/action/protocol/account/transfer.go#L73

What would you like to be added: Enable transfer to a smart contract and trigger fallback function if any

Why is this needed: Be compatible with more dapps

[maswalker]

I think that transfer to contract has already been supported by execution. please refer to the commit, https://github.com/iotexproject/pebble-contracts/commit/122498880907af062b7652ed8801b4f00315227d

[raullenchai]

My testing example

pragma solidity 0.7.3;

contract Receiver {
    event Received(address, uint);
    uint256 cnt = 0;

    function getcount() public view returns (uint256) { 
        return cnt;
    }

    receive() external payable {
        cnt += 1;
        emit Received(msg.sender, msg.value);
    }
}

Verified that every transfer of IOTX to this contract increases count by 1, indicating it works.

[raullenchai]

Pending on #1600