This trait is the extension trait for GenerationalPlan (see Rust’s extension trait pattern).
Generally any method should be put to GenerationalPlan if possible while keeping GenerationalPlan
object safe. In this case, generic methods will be put to this extension trait.
Is current GC only collecting objects allocated since last GC? This method can be called
with any plan (generational or not). For non generational plans, it will always return false.