[quant][graphmode][fx] Move custom_module_class config to prepare/convert_custom_config_dict (#46251)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/46251
Test Plan: Imported from OSS
Reviewed By: raghuramank100
Differential Revision: D24290810
fbshipit-source-id: 7a96f04a0f33f0315943ac18ef2d08e4f5a5d1c0
