Summary:
When multiple files are shared from desktop to android the transfer of the
files should be handled using 1 notification

Depends on: D17081

Test Plan:
Share multiple biggish files from desktop to android
The sharing progress is displayed using 1 notification

Reviewers: #kde_connect, albertvaka

Reviewed By: #kde_connect, albertvaka

Subscribers: kdeconnect

Tags: #kde_connect

Differential Revision: https://phabricator.kde.org/D17157