Extend cuda::std::numeric_limits for __half, __nv_bfloat16, __nv_fp8_e4m3, __nv_fp8_e5m2 and deprecate cub::FpLimits

[bernhardmgruber]

Part of this is covered here: #525

[fbusato]

would make sense to also add the following functions for completeness?

• isfinite
• isinf
• isnan
• isnormal
• signbit

(@davebayer for visibility)

[miscco]

Can we split __nv_fp8_e4m3 and __nv_fp8_e5m2 into their separate issue because we currently do not support them at all in libcu++

[bernhardmgruber]

would make sense to also add the following functions for completeness?

• isfinite
• isinf
• isnan
• isnormal
• signbit

Eventually yes, but I don't need them to deprecate/replace cub::Traits, so they are less urgent IMO.