Created by: luotao1

Now we use AnalysisPredictor::SetMkldnnThreadID() to run MKLDNN multi-instance in unit-tests: https://github.com/PaddlePaddle/Paddle/blob/de42fe8fd584cca4a804e6e6f178f14b169d33c3/paddle/fluid/inference/tests/api/tester_helper.h#L415-L425 However, this interface is not in paddle_analysis_config.h, how do users run MKLDNN multi-instance? If we expose to users? What's the interface? How about config.EnableMKLDNN(int mkldnn_thread_id)?