[PyTorch] Add IValue::toTupleRef() (#65504)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/65504
We should be able to borrow a Tuple from an IValue without incurring refcount bumps.
ghstack-source-id: 142065833
Test Plan:
Added test coverage.
Profiled static runtime on the local_ro net for ctr_mobile_feed. Inclusive time spent in VarTupleUnpack decreased about 0.3%, which roughly matches with the 0.36% of runtime that was previously spent in IValue::toTuple().
Reviewed By: hlu1
Differential Revision: D31130570
fbshipit-source-id: afa14f46445539e449068fd908d547b8da7f402c
