[HybridKV] Fix prefill disaggregation kvcache addr alignment & use hybrid kv cache only when running qwen3_next (#3007)

### What this PR does / why we need it?
This pr fixes a few issues on prefill disaggregation:
1. Fix prefill disaggregation kvcache addr alignment issue, llmdatadist
needs the addr of tensors to be aligned with 2M
2. Fix prefill disaggregation kvcache shape error, llmdatadist requires
k/v tensors with shape [num_blocks, ...], however the implentment before
this pr is [2, num_blocks, ...], which will break prefill disaggregation
3. Use hybrid kv cache only when running qwen3_next to fix accuracy
issue on prefill disaggregation.

### Does this PR introduce _any_ user-facing change?
N/A

### How was this patch tested?
Tested locally by @liziyu179 

- vLLM version: v0.10.2
- vLLM main:
4f02b77de4

---------

Signed-off-by: MengqingCao <cmq0113@163.com>

vllm_ascend/worker/block_table.py

@@ -167,8 +167,7 @@ class BlockTable:
                 mask, slot_mapping, -1)
         else:
             assert self.kernel_sizes is not None
-            if self.block_size == self.kernel_sizes[0] or self.kernel_sizes[
-                    0] == 0:
+            if self.block_size == self.kernel_sizes[0]:
                 # IMPORTANT: In hybrid mode, positions are in logical block space,
                 # but we need to map them to the correct logical block table indices
                 logical_block_idx = positions // self.block_size