1. Rename Dygraph To Static Decorators to declarative
2. dygraph_to_static_func is still using in some training tests, I cannot delete it now.
3. Add some API docs

* supports thread-binding stream, test=develop

* avoid using thread_local variables in dtor, test=develop

* modify the stream priority enum, test=develop

* enhance error message test=develop

* fix CI test of 3 op test=develop

* fix bug caused by the diff of long type in py2 and py3, test=develop

* fix error message of l2_normalize, matmul, mean, etc. 
* add the test case for those ops

* Move BasicApiTransformer to a separate file. test=develop

* Fix a bug: A api in module is not a real dygraph api in dygraph_to_static. test=develop

* improve efficiency of dot op in dygraph mode

* add comments for dot op for dygraph behavior

* fix trt fc fuse test, test=develop

* fix trt_transpose_flatten_concat shape, test=develop

* add addcmul, test=develop

* OP clip, merge_lod_tensor, convert/elementwise error message enhancement. test=develop

test=develop

As the title

* use 32 bit index to improve expand op, test=develop

* remove redundant code, test=develop

* add nll_loss op test=develop

* Weight quantization support channel_wise_abs_max method to achieve higher accuracy

* add paddle.std api test=develop

* update  test=develop

* fix example code format test=develop

* allow amp and recompute working together

API/OP (center_loss, fluid.one_hot, prroi_pool, roi_pool, ctc_greed_decoder) error message enhancement (#23794)

* error message enchanced, test=develop

* error message enchanced for APIs, test=develop

* error message enhanced for roi_pool, test=develop

* update added code, test=develop

* update fluid/input.py, test=develop

* update fluid/input.py ,test=develop

* fix code style, test=develop

* fix lower converage, test=develop

* error message enhanced for roi pool, test=develop

Correct the name [`FLAGS_sync_nccl_allreduce`](https://www.paddlepaddle.org.cn/documentation/docs/zh/advanced_guide/flags/others_cn.html#flags-sync-nccl-allreduce) based on the information from our official website.

As the title.

* fix bug in reduce op test=develop

* fix bug in reduce op test=develop

* API(fused_embedding_fc_lstm) error message enhancement. test=develop

C++ API enhancement.

* Refine code, test=develop

* Refine code. test=develop

Enhance print op c++ error message.

* error message enhancement create_parameter create_global_var, test=develop

* use six.PY2 to use long, test=develop

* fix input dtype for create_parameter, test=develop

Fix the compile problem in norm op in the windows env, add delete some invalid argument