Making test_machine_translation.py supports regularization

[chengduoZH]

Fix #8697

The reason for this bug is that if there are sparse parameters in the model when the regularization is added, some ops' inputs will become sparse data and dense data which is not supported currently.

To fix this bug(test_machine_translation.py will be hung out with regularization), the following tasks need be completed.

• Add ElementwiseOpInferVarType for elementwise_op. Add ElementwiseOpInferVarType for Elementwise_op #8890
• Make elementwise_add_op's input supportting SelectedRows type. Enhance elementwise_add #8935
• Enhace look_up_table op, make it support concat rows. Enhance look_up_table op  #8932
• Fix the regularization code in Python side. Enhance regularizer.py #8934