[StaticRuntime] Clean up input references (#51952)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51952
StaticRuntime should not hold owning refs of inputs after inference is finished. This diff adds a pass to clean them up and unit tests to enforce the check.
Will clean up output tensors in separate diffs.
Test Plan:
```
buck test //caffe2/benchmarks/static_runtime:static_runtime_cpptest
buck test mode/opt-clang caffe2/caffe2/fb/predictor:ptvsc2_predictor_bench_test
```
Reviewed By: bwasti
Differential Revision: D26331506
fbshipit-source-id: d395a295ada9de3033d0ea05d1dbab62d879a03b
