BUG: Fix NaT handling in the PyArray_CompareFunc for datetime and timedelta
BUG: Fix NaT handling in the PyArray_CompareFunc for datetime and timedelta

In #12658 and #15068 the sort ordering for datetime and timedelta was changed
so that NaT sorts to the end, but the internal compare array function was not
updated.

Fixes #19574.

mattip/numpy,endolith/numpy,simongibbons/numpy,mhvk/numpy,mattip/numpy,pdebuyl/numpy,seberg/numpy,endolith/numpy,mhvk/numpy,anntzer/numpy,seberg/numpy,jakirkham/numpy,mhvk/numpy,mhvk/numpy,jakirkham/numpy,pdebuyl/numpy,jakirkham/numpy,jakirkham/numpy,endolith/numpy,charris/numpy,pdebuyl/numpy,pdebuyl/numpy,rgommers/numpy,mhvk/numpy,numpy/numpy,endolith/numpy,numpy/numpy,rgommers/numpy,numpy/numpy,seberg/numpy,anntzer/numpy,simongibbons/numpy,simongibbons/numpy,charris/numpy,numpy/numpy,mattip/numpy,charris/numpy,charris/numpy,jakirkham/numpy,simongibbons/numpy,rgommers/numpy,seberg/numpy,simongibbons/numpy,anntzer/numpy,mattip/numpy,anntzer/numpy,rgommers/numpy