API - add more passes to graph mode (#27093)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/27093
Add `insert_prepack_unpack` and `fold_prepack` to `convert_script`
Test Plan:
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Imported from OSS
Differential Revision: D17678262
fbshipit-source-id: 4bfd6681af6fce226cc77aed8dd84066cbd8ed17
