Stack from ghstack:

• [ONNX] Enable support for roll() op. (#58389) #58582 [ONNX] Enable support for roll() op. ([ONNX] Enable support for roll() op. #58389)
• [ONNX] handle aten::_set_item on Dict in convertInplaceOpsAndTrackAlias (#58317) #58581 [ONNX] handle aten::_set_item on Dict in convertInplaceOpsAndTrackAlias ([ONNX] handle aten::_set_item on Dict in convertInplaceOpsAndTrackAlias #58317)
• [ONNX] use consistent quoting for string literals (#57757) #58580 [ONNX] use consistent quoting for string literals ([ONNX] use consistent quoting for string literals #57757)
• [ONNX] Improve lower tuples and handle control flow (#57650) #58579 [ONNX] Improve lower tuples and handle control flow ([ONNX] Improve lower tuples and handle control flow  #57650)
• [ONNX] Update special post process for SequenceInsert after SequenceEmpty (#56965) #58578 [ONNX] Update special post process for SequenceInsert after SequenceEmpty ([ONNX] Update special post process for SequenceInsert after SequenceEmpty #56965)
• Support symbolic for conv_tbc (#58359) #58577 Support symbolic for conv_tbc (Support symbolic for conv_tbc #58359)
• [ONNX] RNN scripting (#57564) #58576 [ONNX] RNN scripting ([ONNX] RNN scripting #57564)
• [ONNX] Update instance_norm2 symbolic to handle track_running_stats=True (#55051) #58575 [ONNX] Update instance_norm2 symbolic to handle track_running_stats=True ([ONNX] Update instance_norm2 symbolic to handle track_running_stats=True #55051)

ONNX::SequenceEmpty requires dtype to be provided, and is default to float. We updates previous dtype of created ONNX::SequenceEmpty node when dtype is later discovered to be other than float, through downstream ONNX::SequenceInsert node. This PR improves the algorithm to cover nested loop case.

Co-authored-by: BowenBao bowbao@microsoft.com