[main][bugfix] Change seq_lens in dummy attn_metadata to max_query_len (vllm-project#4097)

### What this PR does / why we need it?
Currently, we set `seq_lens` in dummy attn_metadata to be
`max_model_len` to get max workspace for attention during capturing.
However, setting it consistently to be `max_model_len` causing dummy_run
to execute a long attention when running actual inference. For example,
if there is a single req with `seqs_lens` as [8] but `max_model_len` is
131072, the whole process will be slow down by dummy_run as it execute a
fake long-seq attention. Therefore, we instead set it to max_query_len,
which is also consistent with vLLM gpu implementation.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?

- vLLM version: v0.11.0
- vLLM main:
vllm-project/vllm@83f478b

---------

Signed-off-by: Angazenn <[email protected]>
Signed-off-by: luolun <[email protected]>

Author: Angazenn

vllm_ascend/worker/model_runner_v1.py

@@ -2824,7 +2824,7 @@ def _build_dummy_attn_metadata(
 
             attn_metadata = {}
 
-            seq_lens = self.model_config.max_model_len
+            seq_lens = max_query_len
             self.seq_lens_np[:num_reqs] = seq_lens
             self.seq_lens_np[num_reqs:] = 0