[Desktop] Change ThreadID to long

Summary: Change ThreadID to long

Test Plan:
Messages should send and receive as before. Additionally, if your device has assigned extremely large ThreadIDs, the SMS plugin should no longer crash.

This patch corresponds to the Android-side revision D17517

Reviewers: KDE Connect, nicolasfella

Reviewed By: KDE Connect, nicolasfella

Subscribers: nicolasfella, kdeconnect

Tags: KDE Connect

Differential Revision: https://phabricator.kde.org/D17516