[BugFix] Fix lazy imports involving outlines_core (#27158)

Signed-off-by: 22quinn <33176974+22quinn@users.noreply.github.com>

vllm/v1/structured_output/backend_outlines.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright 2025-present the Outlines developers
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+from __future__ import annotations
+
 import ast
 import importlib
 import json

vllm/v1/structured_output/utils.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+from __future__ import annotations
+
 import hashlib
 import importlib.metadata
 import os