Add test/onnx_caffe2 to ONNX Exporter merge rule (#109295)
As we deprecate the TorchScript ONNX exporter we need to refactor the onnx caffe2 tests to start using private functions instead of public ones
That requires changes to the merge rules to allow ONNX exporter to drive deprecation
Pull Request resolved: https://github.com/pytorch/pytorch/pull/109295
Approved by: https://github.com/malfet
