Revert "[ONNX] Move all torch.onnx.export related tests to test/onnx (#87292)"
This reverts commit e3e84830aade59722d819bc5fa01922239494790.
Reverted https://github.com/pytorch/pytorch/pull/87292 on behalf of https://github.com/weiwangmeta due to breaking internal test relating to quantization eager tests, see test/quantization/eager/test_quantize_eager_ptq.py test_lower_graph_linear and test_lower_graph_conv2d
