[zlib] Add ZLIBNG_VERSION (#14513)

Co-authored-by: Brian Schubert <brianm.schubert@gmail.com>

stdlib/@tests/stubtest_allowlists/win32-py314.txt

@@ -1,11 +1,3 @@
-# ====================================================================
-# TODO: New errors in Python 3.14 that need to be fixed or moved below
-# ====================================================================
-
-compression.zlib.ZLIBNG_VERSION
-zlib.ZLIBNG_VERSION
-
-
 # =======
 # >= 3.12
 # =======

stdlib/zlib.pyi

@@ -4,11 +4,11 @@ from typing import Any, Final, final, type_check_only
 from typing_extensions import Self
 
 DEFLATED: Final = 8
-DEF_MEM_LEVEL: int  # can change
+DEF_MEM_LEVEL: Final[int]
 DEF_BUF_SIZE: Final = 16384
-MAX_WBITS: int
-ZLIB_VERSION: str  # can change
-ZLIB_RUNTIME_VERSION: str  # can change
+MAX_WBITS: Final[int]
+ZLIB_VERSION: Final[str]
+ZLIB_RUNTIME_VERSION: Final[str]
 Z_NO_COMPRESSION: Final = 0
 Z_PARTIAL_FLUSH: Final = 1
 Z_BEST_COMPRESSION: Final = 9
@@ -26,6 +26,10 @@ Z_RLE: Final = 3
 Z_SYNC_FLUSH: Final = 2
 Z_TREES: Final = 6
 
+if sys.version_info >= (3, 14) and sys.platform == "win32":
+    # Available when zlib was built with zlib-ng, usually only on Windows
+    ZLIBNG_VERSION: Final[str]
+
 class error(Exception): ...
 
 # This class is not exposed at runtime. It calls itself zlib.Compress.