Add address asset and uint256 amount in the MessageContext on connected chain

[lumtis]

The onCall hook on connected chains has the following object:

struct MessageContext {
    address sender;
}

Amount passed of Ether can be obtained with msg.value but for ERC20 there is no such information, unless it is added manually in the message, but this is an overhead for the developers that shouldn't be necessary
We should add information such as amount and asset to the context:

struct MessageContext {
    address sender;
    address asset;
    uint256 amount;
}

[fadeev]

This is very important! It's possible to add amount to the message, but I don't know if it possible to add the asset address, I don't think there is a mapping on ZetaChain where you can get underlying asset address from ZRC-20.