[SR] Add utility class to determine tensor ranges (#68284)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68284
Add a new class `ManagedTensorRanges` that determines when manage tensors can be made available for re-use. This class provides a method `availableTensors(Node* node)` that returns a vector of `Value*` (corresponding to managed tensors) that are not used (either directly or through any alias) after `node`.
Test Plan: New unit tests: `buck test caffe2/benchmarks/static_runtime:static_runtime_cpptest`
Reviewed By: swolchok
Differential Revision: D32397207
fbshipit-source-id: fb0d9a23f13abf6f2207e3d7266384966f477fc6
