[ONNX] Perform Shape inference on added "Cast" node (#106093)
This commit fixes a bug where some "If" nodes blocked shape inference during the onnx graph building.
In fixup_onnx_controlflow, a "Cast" node is added to conditions in "If" and "Loop" nodes if the condition type is not bool.
This commit performs shape inference on this new "Cast" node which allows its output to be marked as "reliable" in ConstantValueMap during further shape inference. This would have eventually happened when shape inference is performed on the entire graph, but the inferred shapes are also useful to have during onnx graph building, since it allows some ops (like Squeeze) to export into simpler subgraphs.
Also adds a test for this.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/106093
Approved by: https://github.com/thiagocrepaldi
