### What this PR does / why we need it?
Add UT for mooncake
- vLLM version: v0.12.0
- vLLM main:
ad32e3e19c
Signed-off-by: tongyuzhou <tongyuzhou1@huawei.com>
Signed-off-by: wangxiaochao <w00642655@china.huawei.com>
Co-authored-by: tongyuzhou <tongyuzhou1@huawei.com>
Co-authored-by: wangxiyuan <wangxiyuan1007@gmail.com>