test(annotations): one shared folder_paths stub for the API test modules

test_api_images and test_api_prompts installed a MagicMock folder_paths,
so whenever one of them was imported before test_api_autotag the later
patch("folder_paths.get_output_directory") in test_api_history_outputs
left a mock attribute behind and two test_diagnostics_config tests
failed. tests/host_stubs.py now installs one real-module stub, used by
test_api_images, test_api_prompts and test_api_autotag (and through
test_api_images by the annotation modules, whose copy is gone), so the
modules pass in either import order.

tests/test_api_annotations.py

@@ -11,10 +11,8 @@ import hashlib
 import json
 import os
 import sqlite3
-import sys
 import tempfile
 import threading
-import types
 import unittest
 import uuid
 from pathlib import Path
@@ -22,17 +20,6 @@ from unittest.mock import AsyncMock, patch
 
 from aiohttp.test_utils import make_mocked_request
 
-# Discovery imports this module before tests/test_api_autotag.py, whose
-# ``folder_paths`` stub (a real module, so ``patch(..., create=True)`` can add
-# and remove attributes) the later modules rely on. Install the same stub
-# before test_api_images would install a MagicMock in its place.
-if "folder_paths" not in sys.modules:
-    _stub = types.ModuleType("folder_paths")
-    _stub.models_dir = tempfile.gettempdir()
-    _stub.base_path = tempfile.gettempdir()
-    _stub.get_output_directory = tempfile.gettempdir
-    sys.modules["folder_paths"] = _stub
-
 try:
     from test_api_images import ImageAPITestCase, make_png
     from open_handles import assert_closed, open_handles_under