Our old `loop_body` function may return single element when `loop_vars` just contains only 1 element, which can cause bug. The key point of this PR is forcing `loop_body` functions always return tuple.

* Refine saving output scale to infer program

* Delete fast_check_nan_inf

* Delete run_fast_nan_inf_debug

fix launch ps ut test=develop

* nearest_interp op converter w/ dynamic/static

* fix data_layout include

* add trt nearest unit_test

* add nearest_interp NHWC test

* update trt nearest interp nhwc testcase

* remove asterisk for python2 compatibility

* add empty line to prevent conflict

* nearest_interp op converter w/ dynamic/static

* fix data_layout include

* add trt nearest unit_test

* add nearest_interp NHWC test

* update trt nearest interp nhwc testcase

* remove asterisk for python2 compatibility

* add empty line to prevent conflict

* change the priority of out_h, out_w

* add 1f1b scheduler for pp, test=develop

* Fix skip_quant in QAT

* support float16 in custom op

* fix failed unittests

* support attribute in infershape

* polish details

* Refine calculating output scale of dygraph qat, test=develop

* support custom complex op

* fix detail error

* add inference support

* fix setup windows failed

* trt gather converter

* add trt gather unit_test

* fix one ps gradient clip

* remove useless import. test=develop

* add dict/str/list supprot for DataLoader. test=develop

* add serialize unittest

* fix element_op trt plugin serialize bug

* Support loading parameters from checkpoint to save quantized model

* Fix the unittest test_moving_average_abs_max_scale_op

* Add unittest of save_quantized_model from checkpoint

* Add comments to explain the function

* support duplicable op inout

* add costom concat op test

* Fix bug with static_convert_var_shape

* replace dot with dash

* heter bug

* format

* format