test llama4x HF with config parser (#25912)

Summary:

test llama4x with shardist config parser

Test Plan:
buck test //vllm/fb/tests\:test_llama4x_hf -- --print-passing-details
https://www.internalfb.com/intern/testinfra/testconsole/testrun/1970325152656551/

buck test 'fbcode//mode/opt' fbcode//vllm/fb/plugins/tests:test_shardist_loader -- --exact 'vllm/fb/plugins/tests:test_shardist_loader - test_shardist_model_loading (vllm.fb.plugins.tests.test_shardist_loader.TestShardistLoader)' --run-disabled
https://www.internalfb.com/intern/testinfra/testconsole/testrun/844425379106729/

Differential Revision: D83405333

Author: acisseJZhong

vllm/config/model.py

@@ -1334,11 +1334,13 @@ def try_get_generation_config(self) -> dict[str, Any]:
                 self.hf_config_path or self.model,
                 trust_remote_code=self.trust_remote_code,
                 revision=self.revision,
+                config_format=self.config_format,
             )
         else:
             config = try_get_generation_config(
                 self.generation_config,
                 trust_remote_code=self.trust_remote_code,
+                config_format=self.config_format,
             )
 
         if config is None:

vllm/transformers_utils/config.py

@@ -949,6 +949,7 @@ def try_get_generation_config(
     model: str,
     trust_remote_code: bool,
     revision: Optional[str] = None,
+    config_format: Union[str, ConfigFormat] = "auto",
 ) -> Optional[GenerationConfig]:
     try:
         return GenerationConfig.from_pretrained(
@@ -961,6 +962,7 @@ def try_get_generation_config(
                 model,
                 trust_remote_code=trust_remote_code,
                 revision=revision,
+                config_format=config_format,
             )
             return GenerationConfig.from_model_config(config)
         except OSError:  # Not found