Add more defaults to the stdlib (#9606)

Continuing work towards #8988.

The first five commits were created using stubdefaulter on various Python versions; the following commits were all created manually by me to fix various problems. The main things this adds that weren't present in #9501 are:

- Defaults in Windows-only modules and Windows-only branches (because I'm running a Windows machine)
- Defaults in non-py311 branches
- Defaults for float parameters
- Defaults for overloads

stdlib/datetime.pyi

@@ -265,7 +265,7 @@ class datetime(date):
     else:
         @overload
         @classmethod
-        def now(cls: type[Self], tz: None = ...) -> Self: ...
+        def now(cls: type[Self], tz: None = None) -> Self: ...
         @overload
         @classmethod
         def now(cls, tz: _TzInfo) -> datetime: ...