fix(stackable-versioned): Handle fields added in later versions

[Techassi]

Found by @sbernauer

#[versioned(
    version(name = "v1alpha1"),
    version(name = "v1alpha2"),
    version(name = "v1beta1"),
    version(name = "v1")
)]
struct Foo {
    username: String,

    #[versioned(added(since = "v1alpha2"))]
    first_name: String,

    #[versioned(added(since = "v1beta1"))]
    last_name: String,
}