Fix#100718: NLA Hold Forward Inconsistency
Action Track with 'extrapolation=Hold Forward' behaves the same as 'Hold'.
For the Action Track, we now properly treat extrapolation Hold_Forward just like the rest of the NLA system.
Co-author Wayde Moss @wbmoss_dev
Pull Request: https://projects.blender.org/blender/blender/pulls/109182