[LITE][XPU] 1. Add sequence_unpad kernel for XPU; 2. Bugfix in sequence_unpad kernel for x86, as InferShapeImpl() is now empty in lite/operators/sequence_unpad_op.cc; 3. Refine TargetWrapperXPU; (#4237)

* fix typo

* [LITE][XPU] accomodate crmm(variant 20200608)

* refine lite/tests/api/test_mmdnn_lite_xpu.cc

* more comments, test=develop test=xpu

* bugfix in crmm pattern match

* pr comments, test=develop test=xpu

* add XPU_CALL and retval check, test=develop test=xpu

* [LITE][XPU] accomodate resnet_cbam

* [LITE][XPU] accomodate content-dnn

* fix pr comments test=develop

* fix pr comments test=develop

* fix pr comments test=develop test=xpu

* fix compilation error, test=develop test=xpu

* [X86] Fix the unit test of slice op
test=develop test=xpu
Co-authored-by: Nhong19860320 <9973393+hong19860320@users.noreply.github.com>