Delete functorch use_fake_tensor and debug_fake_cross_ref (#99314)
Using fake tensor with AOTAutograd is now mandatory, simplifying our
logic. Unfortunately, this means debug_fake_cross_ref must go,
but I don't think anyone has used it recently.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/99314
Approved by: https://github.com/eellison, https://github.com/zou3519
