Add dynamo config skip_nnmodule_hook_guards (#97830)
This lets users that are sure they won't use hooks avoid overhead
related to dynamo guards on (assumedly) empty hook dicts on all
nn modules.
Only enable this flag if you are sure you won't change hook-behavior
after compiling. It is ok to register a hook and then compile, if
you promise never to remove/alter the hook. It is also ok to
not register a hook and compile, if you never register a hook later.
Note- this is not the best we can do, and hopefully in the future
we can avoid the need for this option following some of these paths
- make guards fast enough to not be an issue when guarding on hook
dicts
- make a mode where dynamo actually skips tracing __call__ so
hooks are consistently ignored by compiled programs
- use nnmodule versioning so hook changes can be guarded without
explicit hook dict guards
Pull Request resolved: https://github.com/pytorch/pytorch/pull/97830
Approved by: https://github.com/jansel
