Add InsertPackUnpack pass (#26959)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/26959
Add insert_pack_unpack pass for future transformations.
Only added a pattern for linear, will need to have a
pattern for conv2d as well
Test Plan:
tbd
Imported from OSS
Differential Revision: D17636400
fbshipit-source-id: 8dc64213aac0f91b55dbe3aafd92c6dce36ddd89
