[quant][eagermode] Move custom_module registration to prepare/convert_custom_config_dict (#46293)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/46293
Test Plan: Imported from OSS
Reviewed By: raghuramank100
Differential Revision: D24290811
fbshipit-source-id: 7d2aee98e1946c2a4268efb94443f1e5daaa793e
