[ONNX] Release values cached in global object (#68210)
Summary:
To release constants computed and stored by `ConstantValueMap::SetValue(...)` during ONNX exporting, `ConstantValueMap::Clear()` needs to be called explicitly. Otherwise, it's a memory leak.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68210
Reviewed By: jansel
Differential Revision: D32465670
Pulled By: msaroufim
fbshipit-source-id: 521e474071b94c5d2cd4f353ee062cee78be1bd4
