[quant][graphmode][fx] Add input_idx_to_dtype and ouptut_idx_to_dtype to backend_config_dict (#67067)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/67067
Plan to gradually adding features to backend_config_dict, this PR adds support
for specifying the dtype for input and output of a given pattern
Test Plan: Imported from OSS
Reviewed By: vkuzo
Differential Revision: D31849074
fbshipit-source-id: ca2fbb873176fe72e08ea79ed1bc659bf27cbd8a
