Stop implementing INIT_SPACE manually

I see that in some parts of the code, we still implement init space manually. Instead, it should be derived with macros. Example: https://github.com/cosmos/solidity-ibc-eureka/blob/28ca34b2c0d7b2838a6da4c3038c23b9d2e8cb83/programs/solana/programs/gmp-counter-app/src/state.rs#L16-L23