Cleanup: use lower-case list and dict, add a test (#6161)

stdlib/multiprocessing/pool.pyi

@@ -1,6 +1,6 @@
 import sys
 from _typeshed import Self
-from typing import Any, Callable, ContextManager, Dict, Generic, Iterable, Iterator, List, Mapping, TypeVar
+from typing import Any, Callable, ContextManager, Generic, Iterable, Iterator, List, Mapping, TypeVar
 
 if sys.version_info >= (3, 9):
     from types import GenericAlias
@@ -17,7 +17,7 @@ class ApplyResult(Generic[_T]):
     else:
         def __init__(
             self,
-            cache: Dict[int, ApplyResult[Any]],
+            cache: dict[int, ApplyResult[Any]],
             callback: Callable[[_T], None] | None,
             error_callback: Callable[[BaseException], None] | None,
         ) -> None: ...
@@ -44,7 +44,7 @@ class MapResult(ApplyResult[List[_T]]):
     else:
         def __init__(
             self,
-            cache: Dict[int, ApplyResult[Any]],
+            cache: dict[int, ApplyResult[Any]],
             chunksize: int,
             length: int,
             callback: Callable[[List[_T]], None] | None,
@@ -55,7 +55,7 @@ class IMapIterator(Iterator[_T]):
     if sys.version_info >= (3, 8):
         def __init__(self, pool: Pool) -> None: ...
     else:
-        def __init__(self, cache: Dict[int, IMapIterator[Any]]) -> None: ...
+        def __init__(self, cache: dict[int, IMapIterator[Any]]) -> None: ...
     def __iter__(self: _S) -> _S: ...
     def next(self, timeout: float | None = ...) -> _T: ...
     def __next__(self, timeout: float | None = ...) -> _T: ...

stdlib/plistlib.pyi

@@ -1,7 +1,7 @@
 import sys
 from datetime import datetime
 from enum import Enum
-from typing import IO, Any, Dict as _Dict, List, Mapping, MutableMapping, Tuple, Type
+from typing import IO, Any, Dict as _Dict, Mapping, MutableMapping, Tuple, Type
 
 class PlistFormat(Enum):
     FMT_XML: int
@@ -31,7 +31,7 @@ else:
     ) -> Any: ...
 
 def dump(
-    value: Mapping[str, Any] | List[Any] | Tuple[Any, ...] | str | bool | float | bytes | datetime,
+    value: Mapping[str, Any] | list[Any] | Tuple[Any, ...] | str | bool | float | bytes | datetime,
     fp: IO[bytes],
     *,
     fmt: PlistFormat = ...,
@@ -39,7 +39,7 @@ def dump(
     skipkeys: bool = ...,
 ) -> None: ...
 def dumps(
-    value: Mapping[str, Any] | List[Any] | Tuple[Any, ...] | str | bool | float | bytes | datetime,
+    value: Mapping[str, Any] | list[Any] | Tuple[Any, ...] | str | bool | float | bytes | datetime,
     *,
     fmt: PlistFormat = ...,
     skipkeys: bool = ...,