feat: Support unconstrained public functions

[LHerskind]

Currently unconstrained execution UnconstrainedFunctionExecution don't support accessing public storage which makes it quite painful to read public storage as you then need to do it by computing storage slots and handle that yourself.

We should extend the unconstrained execution such that it have access to public storage.

For a noir function

unconstrained fn publicBalanceOf(
    owner: Field,
) -> Field {
    let storage = Storage::init();
    let owner_balance = storage.balances.at(owner);

    owner_balance.read()
}

We should be able to run the following without handing out errors as goldstars in a kindergarden.

const balance = await contract.methods.publicBalanceOf(recipient.toField()).view();