[BUG]: Remove all wrong usages of cuda:: and std:: namespace in CUB

[fbusato]

Is this a duplicate?

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

Area

CUB

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

• cuda::std is used without the full namespace ::cuda::std in several places
• std:: is used instead of ::cuda::std

Describe the solution you'd like

fix the namespaces

Describe alternatives you've considered

No response

Additional context

No response

[bernhardmgruber]

Mind that there are some uses of std:: that are justified. std::iterator_traits is one example.