Fix onnx export

Fix

• ONNX import for
  • Squeeze
• ONNX export for
  • Squeeze
  • UnSqueeze
  • Slice
  • ConstantOfShape
  • GenericOp
  • BatchNorm

Update

• Improve onnx export to support graph that has already been forward_dims (without using inputs/outputs_dims)
• Remove some usage of verbose to use Log.info instead