[Static Runtime] Add FuseListUnpackV2 (#66509)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66509
Like `FuseListUnpack`, but instead of adding arguments to the fused node's outputs, inserts a new fused op.
By using a new fused op, we can avoid runtime `is_fused` checks. This will make the op implementations significantly cleaner. Eventually, we will migrate all ops to `V2` and delete to old pass.
`FuseListUnpackV2` also fixes the bug described in T103159043.
Test Plan: I've made some changes to D31550307 locally and verified that everything works.
Reviewed By: hlu1
Differential Revision: D31492017
fbshipit-source-id: 4f90fcbc17e4c70a3d65985bee836fabf868a22c
