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

* fix inference c api lod, test=develop

* fix capi lod problem and enrich tests, test=develop

* delete useless header files and alter const_cast, test=develop

* refine pointer and c-api prototype, test=develop

* fix new c api profile bug, test=develop

* add unit tests, test=develop

* support  golang inference

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