make `Base.uabs` public 2 (#53503)
`Base.uabs` is helpful when writing code that works with generic
integers without worrying about silent overflows or overflow errors when
using integers from
[SaferIntegers.jl](https://github.com/JeffreySarnoff/SaferIntegers.jl)
`Base.uabs` is already being used by a few packages
https://juliahub.com/ui/Search?q=uabs&type=code&w=true and has a
docstring. However, it is currently an internal function.
Ref: https://github.com/JeffreySarnoff/SaferIntegers.jl/pull/41
Copy of #53376
