Tweak dynamic=False behavior (#105715)
Previously, dynamic=False is a no-op, and dynamic=True preemptively
turns on dynamic shapes everywhere.
Now, dynamic=False *disables* automatic dynamic, and an unset dynamic
defaults to dynamic=None (which uses automatic dynamic.) This
seems to be more intuitive per
https://github.com/pytorch/pytorch/issues/105634#issuecomment-1644883477
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/105715
Approved by: https://github.com/voznesenskym
