This reverts commit 02083bda.

* Add mkldnn bfloat16 option to C-API

* Add test for bfloat16 gpu

* Change coverage test

* Remove the NGraph engine from PDPD repository
1. Each operator was removed from the operator's directory
2. Each test was removed from the unittest directory
3. The parallel executor support was removed from the PDPD
4. The CMake file was removed from the PDPD
5. The NG flags were removed from the repository
test=develop

* Remove ngraph from:
1. Cmake file
2. Python file
test=develop

* support  golang inference

* fix the PD_ZeroCopyPredictorRun output problem and add some checks and logs for users

* modify the cmakelists depends and fix the cmakelists problem

* add capi for fluid inference api, including AnalysisConfig, AnalysisPredictor, PaddleBuf, PaddleTensor, ZeroCopyTensor