[Test] Add ut for files in /attention (vllm-project#1944)

### What this PR does / why we need it?
Add ut for files in folder /attention
### Does this PR introduce _any_ user-facing change?
No


- vLLM version: v0.10.0
- vLLM main:
vllm-project/vllm@139a7f0

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Signed-off-by: lwq <[email protected]>
Co-authored-by: lwq <[email protected]>

Author: SunnyLee151064