Port libksieve from ktcpsocket to QSslSocket

Summary: port to QSslSocket

Test Plan: run

Reviewers: vkrause, dvratil, dfaure

Reviewed By: vkrause, dfaure

Subscribers: dfaure, kde-pim

Tags: #kde_pim

Maniphest Tasks: T11578

Differential Revision: https://phabricator.kde.org/D24047