Correct the use of DeviceContext in unittest sequence_pooling_test and sequence_padding_test (#22456)

* Add log in memory::Copy for debug purpose.

* Change to use context in DeviceContextPool directly in sequence_pooling_test, instead to new one.

* Change to use context in DeviceContextPool directly in sequence_padding_test, instead to new one.
test=develop

* Change the type of second_dim from size_t to int64_t.
test=develop

* Fix cpplint issues in sequence_padding

* Fix typo in cu file

* Fix dependencies of sequence_padding

* Add include

* Fix CPPLint issue in test_engine

* Fix CPPLint errors in operators/math

* Fix compilation

* Update tensor_util.h

* Update with moved TensorDesc

* Fix tensur_utils.cu

* Update

* Update

* Update

* Update

* Make tensor_util.cu a symbolic link

* Add Seq2BatchFunctor, which will be used in WarpCTCOp.

* Implement WrapCTCFunctor and WrapCTCKernel.

* Add unittest of warpctc_op.

* Modify the check_output inferface in python unittest framework to allow check a subset of outputs.

* Use absolute offset lod in warpctc_op and related functors.

* Refine the comments of warpctc_op.

* The new python unittest supports checking a subset of the outputs, so revoke the previous change.

* Rename the transform from LoDTensor to Tensor with shape [max_sequence_length, num_sequences, sequence_width] to PaddingSequenceFunctor.

* Update to the newest codes.

* Rename the PaddingSequenceFunctor to PaddingLoDTensorFunctor and remove the computation of dimensions out of the functos.