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.

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

* support float16 in custom op

* fix failed unittests

* support attribute in infershape

* polish details

* 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

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

* add serialize unittest

* fix element_op trt plugin serialize bug

* support duplicable op inout

* add costom concat op test

* Fix bug with static_convert_var_shape

* replace dot with dash

* add softmax_switch for softmax_with_cross_entropy_op, test=develop

* delete using EigenMatrix in softmax_with_cross_entropy_op.h, test=develop

* add REGISTER_OP_VERSION for softmax_switch attr of softmax_with_cross_entropy_op, test=develop

* fix bug with jit.save

* refine code

* remove the send/recv of tensor size, but users have to specify the shape of the received var explicitly.

* bugfix for test_cholesky_op

* bugfix for test_compare_op

* bugfix for lookup_table_op

* bugfix for affine_channel_op

* auto specify PADDLE_WITH_MKLDNN and remove Interpretper

* remove print

* fix check abi

* fix windows

* fix compile flags

[Kunlun]Multi xpu dygraph performance optimization , add distributed.spawn support for multi xpu and some bug-fixes (#31130)