[bugfix] Fixing KV Pool Memory Retention and Performance Degradation Issues (#5751)

### What this PR does / why we need it?
1.Fixed memory retention on certain GPUs caused by missing PUT
operations.

2.Fixed performance degradation resulting from architectural
incompatibilities in the underlying refactor.
### Does this PR introduce _any_ user-facing change?

### How was this patch tested?

- vLLM version: v0.13.0
- vLLM main:
2f4e6548ef

---------

Signed-off-by: fems14 <1804143737@qq.com>

vllm_ascend/distributed/kvpool/config_data.py

@@ -223,6 +223,8 @@ class LoadSpec:
     # Whether the scheduler allow us to load the tokens
     can_load: bool
 
+    token_len: int = 0
+
 
 @dataclass
 class RequestTracker: