### What this PR does / why we need it?
This PR refactors `get_kv_cache_spec` method to delegate AttentionSpec
creation to each attention module's own `get_kv_cache_spec()` method,
aligning with the vllm source code structure.
**Changes:**
- Simplify `get_kv_cache_spec` in `model_runner_v1.py` and
`cpu_offload_connector.py`
- Remove manual `AttentionType` checks for `Attention` modules
- Delegate spec creation to each attention module's `get_kv_cache_spec`
method directly
- Let `MambaBase` layers use their own `get_kv_cache_spec` method
- Keep `use_sparse` hack for `MLAAttention` (DeepSeek DSA mode) as
Ascend-specific handling
This change follows RFC #5463 item 12: move AttentionSpec to Attention
module.
- Fixes#5463 (item 12)
### Does this PR introduce _any_ user-facing change?
No. This is an internal refactoring that simplifies code structure
without changing any external behavior.
### How was this patch tested?
- Syntax validation passed via `python -m py_compile`
- CI tests will verify the changes work correctly with existing test
cases
- vLLM version: v0.13.0
- vLLM main:
2f4e6548ef
Signed-off-by: lico67373 <918688502@qq.com>
687df88151