[Refactor] Rename cudagraph_support to aclgraph_support (#3104)

### What this PR does / why we need it?
Updates the `cudagraph_support` attribute to `aclgraph_support` to use
terminology appropriate for the Ascend platform (ACL graphs instead of
CUDA graphs).

This change also explicitly disables graph support for the MLA attention
backend.

### Does this PR introduce _any_ user-facing change?
None.

### How was this patch tested?
None needed.

- vLLM version: v0.10.2
- vLLM main:
5aeb925452

Signed-off-by: Yizhou Liu <liu_yizhou@outlook.com>

vllm_ascend/worker/model_runner_v1.py

@@ -3259,8 +3259,8 @@ class NPUModelRunner(LoRAModelRunnerMixin):
                 builder = attn_group.metadata_builder
             else:
                 builder = attn_group.get_metadata_builder()
-            if builder.cudagraph_support.value < min_ag_support.value:
-                min_ag_support = builder.cudagraph_support
+            if builder.aclgraph_support.value < min_ag_support.value:
+                min_ag_support = builder.aclgraph_support
                 min_ag_builder_name = builder.__class__.__name__
 
         # This is an imitation of compilation_config.splitting_ops_contain_attention()