Infinite loop in `email._header_value_parser._fold_mime_parameters` when parameter names are too long

Bug report

Bug description:

Tested with 3.6 and 3.13.1

>>> import email.message
>>> message = email.message.EmailMessage()
...
>>> message.add_attachment('Hello World!', filename='hello.txt', params={130 * 'A': 'too long parameter name'})
None
>>> message.defects
[]
>>> message
<email.message.EmailMessage object at 0x7fe78ec74ec0>
>>> message.as_string()

130 characters for a media type parameter name is (a bit) more than https://datatracker.ietf.org/doc/html/rfc6838#section-4.3 allows but I didn't expect it to lead into an infinite loop. I wanted to check if the email module would catch that defect, which apparently it doesn't.

Distribution is openSUSE Leap 15.6, python 3.13.1 was installed from pyenv, 3.6 is from the distribution. The python3.11 binary from the distribution exhibits the same behaviour.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-138226
• gh-138227
• gh-138231

Reproduce el problema con email.message.EmailMessage.add_attachment y un nombre de parámetro de 130 caracteres; después inspecciona email._header_value_parser._fold_mime_parameters. Revisa la discusión del issue relacionado y los PRs enlazados antes de continuar. Se considera terminado cuando la entrada ya no queda en un bucle infinito y la cobertura de regresión verifica el comportamiento resultante.