HeaderParseError on email address ending with '.'

Bug report

from email.headerregistry import Address
a = Address("Jane Doe", addr_spec="jane_doe@example.org.")
[…]
HeaderParseError: expected atext but found ''

The issue is the trailing dot, which is arguably not great, but it's very valid actually, and the email address provided is the same as the email address without a dot.

Your environment

• CPython versions tested on: 3.11.1-1 on Debian unstable
• Operating system and architecture: Debian unstable, amd64

Linked PRs

• gh-151972

使用 reproducer 从 email.headerregistry.Address 开始，检查处理 addr_spec 末尾句点的标头解析路径。将其行为与不带句点的等效地址进行比较，并查看关联的 PR gh-151972；完成的标准是，有效的末尾带句点地址不再引发 HeaderParseError，并且有回归测试覆盖。