* error message of NCE API enhancement

Fix the bug of matmul test_case

* fix no_grad signature
test=develop

* check func name instead of doc
test=develop

* API(program_guard) error message enhancement test=develop

* fix Cycle import test=develop

* polish code according comment test=develop

* refine fusion_transpose_flatten_concat_op log
test=develop

* fix ci error
test=develop

* Layer add training attr, add Dropout Layer

* add unit test for Dropout
test=develop

* minor fix
test=develop

* add missing args
test=develop

* support global flag in dropout, add docs
test=develop

* minor fix
test=develop

* minor fix
test=develop

* refine code comments
test=develop

* refine Dropout
test=develop

* fix ut
test=develop

* arg expansion
test=develop

* sample code update
test=develop

* prop -> p
test=develop

* fix ut
test=develop

* minor check fix
test=develop

C++ error message enhancement.

API/OP (ConditionalBlock) error message enhancement (#23480)

* improve error messages of fake_quantize op. test=develop

* update the bit_length error info. test=develop

* install mpi in Dockerfile for coverage ci in xiaolvyun
* test=develop

* 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

* API(fluid.gridents) error message enhancement test=develop

* fix unitest failed test=develop

error message enhancement for repeated fc

fill op error message enhancement

* fix init_gflags with 'python -c', test=develop

* fix pruned_program_cache_key of Operator, test=develop

* polish api program error message, test=develop

* fix condition error, test=develop

* fix test prune error, test=develop

* fix coverage problem, test=develop