datetime.datetime.now() returns wrong time on Windows when env var TZ is set

Bug report

Bug description:

Europe/Berlin is UTC+2 right now, not UTC+1

Works fine on Linux OSes (builds).

C:\Users\work>python
Python 3.12.6 (tags/v3.12.6:a4a2d2b, Sep  6 2024, 20:11:23) [MSC v.1940 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.environ['TZ'] = 'Europe/Berlin'
>>> import datetime
>>> datetime.datetime.now()
datetime.datetime(2024, 9, 20, 12, 15, 24, 771320)
>>> datetime.datetime.now(tz=datetime.UTC)
datetime.datetime(2024, 9, 20, 11, 15, 45, 162005, tzinfo=datetime.timezone.utc)
>>>

CPython versions tested on:

3.12

Operating systems tested on:

Windows

首先，在将 TZ 设置为 Europe/Berlin 的 Windows 上复现所报告的 Python 3.12 行为，并比较 datetime.datetime.now() 与 datetime.datetime.now(tz=datetime.UTC)。跟踪涉及的 datetime 和 Windows 时区处理；当本地时间反映正确的柏林偏移量，并且该行为有回归测试覆盖时，即视为完成。