Fix contract storage analysis for init()

[anton-trunov]

contract Tester {
    x: Int;

    init() { self.x = 42 }

    receive() { } // does not modify the contract state, but we need to save it when `init()` is called

    get fun x(): Int { return self.x }
}

[anton-trunov]

The code above is essentially the following one with everything explicit:

contract Foo(
    lazyDeploymentDone: Bool;
    x: Int;
) {
    fun init() {
        if (!lazyDeploymentDone) {
            self.x = 42;
            self.lazyDeploymentDone = true
        }
    }

    receive() {
        self.init();
    }
}

So, any contract with init() won't benefit from the contract storage optimization, since any receiver needs to store the contract state.