ABIs do not inherit constants from their superABIs

[anton-trunov]

This issue is essentially the same as #4867. We have planned to resolve it after #4272 is merged.

The following piece of code should compile (but it does not at the moment):

contract;

abi MySuperAbi {
    const SUPER_ABI_CONSTANT: u64;
    fn super_abi_method() -> u64;
}

abi MyAbi : MySuperAbi {
    fn abi_method() -> u64;
}

impl MySuperAbi for Contract {
    const SUPER_ABI_CONSTANT: u64 = 42;
    fn super_abi_method() -> u64 { Self::SUPER_ABI_CONSTANT }
}

impl MyAbi for Contract {
    fn abi_method() -> u64 { Self::SUPER_ABI_CONSTANT }
}