stubs/pyfakefs/fake_filesystem_unittest.pyi: Add typing for @patchfs

Add a stub for the @patchfs decorator of this module.

Signed-off-by: Bernhard Kaindl <bernhard.kaindl@cloud.com>

Author: bernhardkaindl

stubs/pyfakefs/fake_filesystem_unittest.pyi

@@ -1,2 +1,20 @@
-from _typeshed import Incomplete
+from types import ModuleType
+from typing import Any, Callable, Dict, List, Optional, Union
+
+from _typeshed import Incomplete  # pylint: disable=import-error
+
 Patcher = Incomplete
+PatchMode = Incomplete
+
+def patchfs(
+    _func: Optional[Incomplete] = ...,
+    *,
+    additional_skip_names: Optional[List[Union[str, ModuleType]]] = ...,
+    modules_to_reload: Optional[List[ModuleType]] = ...,
+    modules_to_patch: Optional[Dict[str, ModuleType]] = ...,
+    allow_root_user: bool = ...,
+    use_known_patches: bool = ...,
+    patch_open_code: PatchMode = ...,
+    patch_default_args: bool = ...,
+    use_cache: bool = ...,
+) -> Callable[[Any], Any]: ...