[stdlib] Deprecate old functions (#14553)

* [stdlib] Deprecate many functions

* Fix typo

* Imporove message for asyncio/trsock

* Apply suggestions from code review

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

* Add Python before version

* [pre-commit.ci] auto fixes from pre-commit.com hooks

* Wrap comment lines

* fix the rest

---------

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

stdlib/_tkinter.pyi

@@ -1,7 +1,7 @@
 import sys
 from collections.abc import Callable
 from typing import Any, ClassVar, Final, final
-from typing_extensions import TypeAlias
+from typing_extensions import TypeAlias, deprecated
 
 # _tkinter is meant to be only used internally by tkinter, but some tkinter
 # functions e.g. return _tkinter.Tcl_Obj objects. Tcl_Obj represents a Tcl
@@ -84,6 +84,7 @@ class TkappType:
     def record(self, script, /): ...
     def setvar(self, *ags, **kwargs): ...
     if sys.version_info < (3, 11):
+        @deprecated("Deprecated since Python 3.9; removed in Python 3.11. Use `splitlist()` instead.")
         def split(self, arg, /): ...
 
     def splitlist(self, arg, /): ...