Derive Macro orzir_macros::ControlFlow

#[derive(ControlFlow)]
{
    // Attributes available to this derive:
    #[successor]
}

Implement the ControlFlow for the given struct.

The #[successor] attribute is used to specify the successor field of the struct.

There are currently two ways to specify these fields:

1. Using the #[successor(n)] where n is the index of the field.
2. Using the #[successor(...)], which means the field is a vector of the successors.

The type of the fields should be Successor or Vec<Successor>.