[PyTorch][JIT] Less shared_ptr use in dictConstruct (#54110)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/54110
dictConstruct doesn't need to make its caller have a `shared_ptr<DictType>`. It also doesn't need to do extra `shared_ptr` copies into the `key_type` and `value_type` locals.
ghstack-source-id: 124150642
Test Plan: fitsships
Reviewed By: ezyang
Differential Revision: D27101782
fbshipit-source-id: 3c632ad9d8f1bd7bdf37f517a86aca27bd41548a
