Deprecate the KTcpSocket-based variant of SslUi::askIgnoreSslErrors

Summary:
The KSslErrorUiData variant below covers KTcpSocket too as a source
for errors, next to QSslSocket/QNAM.

Also, add minimal API docs in here so this shows up on api.kde.org at
all.

Reviewers: dfaure

Reviewed By: dfaure

Subscribers: kde-frameworks-devel

Tags: Frameworks

Maniphest Tasks: T11544

Differential Revision: https://phabricator.kde.org/D24675