Send notification actions

Summary:
Store PendingIntents from notification actions. Send list of notifications to desktop and trigger Intent when matching packet arrives.
CCBUG: 366475

Test Plan: Create test notification, trigger package is received correctly. Whether intent.send() is actually successful is NOT yet tested.

Reviewers: KDE Connect, sredman

Reviewed By: KDE Connect, sredman

Subscribers: sredman, apol, MatMaul, kdeconnect, mtijink, KDE Connect

Tags: KDE Connect

Differential Revision: https://phabricator.kde.org/D12294