[1/2/N] Enable pymarkdown and python __init__ for lint system (#2011)

### What this PR does / why we need it?
1. Enable pymarkdown check
2. Enable python `__init__.py` check for vllm and vllm-ascend
3. Make clean code

### How was this patch tested?


- vLLM version: v0.9.2
- vLLM main:
29c6fbe58c

---------

Signed-off-by: wangli <wangli858794774@gmail.com>

benchmarks/scripts/perf_result_template.md

@@ -28,4 +28,4 @@
 - Models: Qwen/Qwen3-8B, Qwen/Qwen2.5-VL-7B-Instruct
 - Evaluation metrics: throughput.
 
-{throughput_tests_markdown_table}
+{throughput_tests_markdown_table}