[small][batch invariance] Rename the env and internal flags to simplify usage (#26855)

Signed-off-by: Bram Wasti <bwasti@meta.com>

vllm/config/model.py

@@ -21,7 +21,7 @@ from vllm.config.scheduler import RunnerType
 from vllm.config.utils import assert_hashable, config, getattr_iter
 from vllm.logger import init_logger
 from vllm.model_executor.layers.batch_invariant import (
-    vllm_kernel_override_batch_invariant,
+    vllm_is_batch_invariant,
 )
 from vllm.platforms import current_platform
 from vllm.transformers_utils.config import (
@@ -423,7 +423,7 @@ class ModelConfig:
         video_pruning_rate: float | None,
     ) -> None:
         # Enable batch invariance settings if requested
-        if vllm_kernel_override_batch_invariant():
+        if vllm_is_batch_invariant():
             self.enforce_eager = True
 
         # Set the default seed to 0 in V1.