gh-88574: Handle extra blank response line in imaplib

[jrlevine]

Some (buggy) IMAP servers add an extra blank line after a literal value, which makes imaplib throw an exception. This ignores the blank line.
MacOS mail and T'bird can deal with the blank line so it seems to be a somewhat common server bug.

https://bugs.python.org/issue44408

• Issue: imaplib fails when server sends extra blank line after literal value #88574

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[github-actions]

This PR is stale because it has been open for 30 days with no activity.

[serhiy-storchaka]

Please add tests and a news entry.

[bedevere-app]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[serhiy-storchaka]

Oh, and the PR should be against the main branch.

[zware]

This, like GH-26709, also looks like a reasonable change, but also needs to be recreated against main.