### What this PR does / why we need it?
This pull request significantly refactors the attention mechanism for
the Ascend 310P hardware, enhancing its architecture by separating mask
generation concerns from the core attention implementation. It
introduces a dedicated mask builder class capable of handling various
mask types, including causal, splitfuse, and sliding window attention
masks, all optimized for the NPU's fractal data format. This change not
only cleans up the codebase but also lays the groundwork for more robust
and feature-rich attention operations on Ascend devices, backed by new,
extensive unit tests.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
E2E test with qwen3 and qwen3-moe
- vLLM version: v0.15.0
- vLLM main:
d7e17aaacd
---------
Signed-off-by: pu-zhe <zpuaa@outlook.com>
4f33e25046