[Static Runtime] Use IValue::toListRef for aten::len to address comment on D34705231 (#74192)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/74192
This change uses toListRef() to avoid creating a new list object for `aten::len` to address hlu1's comment on D34705231 (https://github.com/pytorch/pytorch/commit/87564a1bd7ab2843e51e1502705c56b860138724)
Test Plan: Existing tests, StaticRuntime.Len*
Reviewed By: mikeiovine
Differential Revision: D34863266
fbshipit-source-id: 65daf36944a64dfd7afde1103aab5aee1681ac87
(cherry picked from commit 3a0f3798f2fcc203f6cb01e59b91e195ecabe1bc)
