### What this PR does / why we need it?
Adjust request map pop time.This pull request optimizes the KV cache
transfer mechanism by streamlining how requests are tracked and cleaned
up. By removing unnecessary mapping structures and adjusting the timing
of request removal, the system achieves more efficient state management
during the transfer process.
pick-from:https://github.com/vllm-project/vllm-ascend/pull/7855
### How was this patch tested?
By ci
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Signed-off-by: wangxiaoteng <wangxiaoteng@huawei.com>
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