Import NN directly rather than lazily throughout the Sage library #34652
Description
This is extracted from #16522.
One issue raised on that ticket is that it is problematic to use lazy imports on things other than a function (stated in #16522 comment:20). It appears that using honest imports rather than lazy ones for NN should not cause too much of a slowdown, but this needs to be tested.
Component: misc
Author: John Palmieri
Branch/Commit: 539119b
Reviewer: Matthias Koeppe
Issue created by migration from https://trac.sagemath.org/ticket/34652