freezing w aot (#105497)
Freezing will take parameters and turn them into constants. A couple changes here:
- move the setting of `flat_params[dropped_index]` before cpp compilation so that cpp_wrapper knows they have been dropped
- compile_fx_aot is doesn't use aot_autograd for invocation, so we no longer add the wrapper which discards dropped param indices. Continuing to add arguments everywhere didn't seem great, so I added `_in_aot_compilation`, but maybe reviewers would prefer something else.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/105497
Approved by: https://github.com/desertfire
