Convert decimals between Substrate native token and EVM native token

[xlc]

The Substrate native token is using 10 (ACA) and 12 (KAR) decimals. All Ethereal tooling assume native token is using 18 decimals.

So when query native token balance, should add the extra zeros. When perform transfer, it should error if the reminder part is not zero and then scale down to the right decimals.

Note the ERC20 precompiles should not be changed.