[DOC]: Create a standalone page for Fancy iterators in CUB

[rwgk]

Is this a duplicate?

• I confirmed there appear to be no duplicate issues for this bug and that I agree to the Code of Conduct

Is this for new documentation, or an update to existing docs?

New

Describe the incorrect/future/missing documentation

https://nvidia.github.io/cccl/cub/ has this near the top:

> Utilities
    > Fancy iterators

But nothing to click on, and neither "fancy" nor "iterator" appear anywhere else in that page.

If this is a correction, please provide a link to the incorrect documentation. If this is a new documentation request, please link to where you have looked.

No response