Update incorrect or incomplete constants in distutils (#12536)

stdlib/distutils/command/install.pyi

@@ -1,11 +1,15 @@
+import sys
 from collections.abc import Callable
-from typing import Any, ClassVar
+from typing import Any, ClassVar, Final
 
 from ..cmd import Command
 
 HAS_USER_SITE: bool
 SCHEME_KEYS: tuple[str, ...]
-INSTALL_SCHEMES: dict[str, dict[Any, Any]]
+INSTALL_SCHEMES: Final[dict[str, dict[str, str]]]
+
+if sys.version_info < (3, 10):
+    WINDOWS_SCHEME: Final[dict[str, str]]
 
 class install(Command):
     description: str

stdlib/distutils/debug.pyi

@@ -1 +1,3 @@
-DEBUG: bool | None
+from typing import Final
+
+DEBUG: Final[str | None]

stubs/setuptools/setuptools/_distutils/sysconfig.pyi

@@ -1,10 +1,10 @@
-from typing import Literal, overload
+from typing import Final, Literal, overload
 from typing_extensions import deprecated
 
 from setuptools._distutils.ccompiler import CCompiler
 
-PREFIX: str
-EXEC_PREFIX: str
+PREFIX: Final[str]
+EXEC_PREFIX: Final[str]
 
 @overload
 @deprecated("SO is deprecated, use EXT_SUFFIX. Support will be removed when this module is synchronized with stdlib Python 3.11")