[ONNX] Deprecate setter functions for global variables (#85165)
`_set_opset_version` and `_set_operator_export_type` are previously deprecated. This PR decorates them with the deprecation decorator, so warnings are emitted.
- Remove usage of `_set_opset_version` and `_set_operator_export_type` in favor of setting the globals vars directly in torch.onnx internal
- Update `GLOBALS.operator_export_type`'s default to not be None to tighten types
- Remove usage of `_set_onnx_shape_inference`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/85165
Approved by: https://github.com/BowenBao, https://github.com/AllenTiTaiWang
