[Performance]: Custom AscendC Kernel of Multi-Step Prepare Input (#814)

### What this PR does / why we need it?

- According to https://github.com/vllm-project/vllm-ascend/issues/807,
we pull request for customer ascendc kernel of multi-step.
- also a bug we found in multi_step_runner.py is fixed when we use
multi-step on V0 Engine.


### Does this PR introduce _any_ user-facing change?

no user-facing change


### How was this patch tested?
we add Unit Test file and offline inference file to test the custom
ascendc kernel. See test/ops/test_multi_step.py and
examples/offline_multi_step.py

---------

Signed-off-by: wan_danfeng <wonderful199082@126.com>

CMakeLists.txt

@@ -45,7 +45,7 @@ endif()
 
 include(${ASCENDC_CMAKE_DIR}/ascendc.cmake)
 file(GLOB KERNEL_FILES
-${CMAKE_CURRENT_SOURCE_DIR}/csrc/kernels/pos_encoding_kernels.cpp)
+${CMAKE_CURRENT_SOURCE_DIR}/csrc/kernels/*.cpp)
 
 ascendc_library(vllm_ascend_kernels SHARED
     ${KERNEL_FILES}