[5/N][CI/UT]add spec decode e2e UT && fix chunk prefill bug

Co-authored-by: mengwei805 <mengwei25@huawei.com>
Co-authored-by: XWFAlone <xuewenfei2@huawei.com>
Signed-off-by: mengwei805 <mengwei25@huawei.com>

Author: mengwei805

.github/workflows/vllm_ascend_test.yaml

@@ -149,7 +149,7 @@ jobs:
         if: steps.filter.outputs.speculative_tests_changed
         run: |
           pytest -sv tests/spec_decode/e2e/test_mtp_correctness.py
-          pytest -sv tests/spec_decode --ignore=tests/spec_decode/e2e/test_mtp_correctness.py 
+          pytest -sv tests/spec_decode --ignore=tests/spec_decode/e2e/test_mtp_correctness.py
 
       - name: Run vllm-project/vllm test
         run: |