Add a pass to fetch attributes of nn.Module to fx.node (#47935)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47935
Fetch the parameters that are needed for lowering from nn.Module to fx.node for leaf_modules.
Test Plan: A test `test_fetch` is added to test_fx_experimental.py.
Reviewed By: jfix71
Differential Revision: D24957142
fbshipit-source-id: a349bb718bbcb7f543a49f235e071a079da638b7
