email.utils.formataddr incorrect handling of unicode names with comma

Bug report

When email.charset is configured to produce 8bit content, calling email.utils.formataddr can result in corrupted output from formataddr. Here's example code:

import email.charset
import email.utils

email.charset.add_charset('utf-8', None)
print("To: " + email.utils.formataddr(('Foo, Bar', 'foo@example.com')))
print("To: " + email.utils.formataddr(('Fôo, Bar', 'foo@example.com')))

Expected output:

To: "Foo, Bar" <foo@example.com>
To: "Fôo, Bar" <foo@example.com>

Actual output:

To: "Foo, Bar" <foo@example.com>
To: Fôo, Bar <foo@example.com>

Your environment

• CPython versions tested on: 3.11.1
• Operating system and architecture: Fedora 37 x86_64

Linked PRs

• gh-155881

Start by running the supplied email.charset and email.utils.formataddr reproduction on CPython 3.11.1, then inspect formataddr's handling of non-ASCII display names containing commas. Done means the output matches the two expected To lines and a regression test covers the configured 8bit case.