[ENHANCEMENT]: Add a callback to the bulk_insert functions

Is your feature request related to a problem? Please describe.

I would like to be able to run a function on every key that is inserted by the bulk insert functions.

Describe the solution you'd like

struct MyFunctor {
  void operator()(slot_type *slot, bool is_unique) {
    ...
  }
};

my_set.insert(input.begin(), input.end(), MyFunctor());

Each insert will return the slot and whether this was an insert or the key was already there so this was just a lookup. And then I will do whatever I want with that information. For example, I could use an atomic and fill an array with unique elements, allowing me to perform "retrieve_all" during the insert without reading the table twice.

Describe alternatives you've considered

I can copy and paste all the bulk insert code into my code and then use that. The problem here is that I trust cuco to get the grid shape and everything right and if I do it this way then I might get it wrong. Also, if cuco comes up with improvements to the bulk insert, I could use them.

Additional context

No response

Start by locating the bulk_insert functions and reviewing the existing insert APIs in cuCollections. Determine how a callback could receive the inserted slot and whether the key was already present, then define tests showing the callback behavior for both new and duplicate keys.