Summary:
Sequentially receiving multiple files was overly complicated sometimes leading to a progress
notification being shown indefinitely. When files are shared using an older kdeconnect-kde version
fallback to receiving each file individually

Test Plan:
Send multiple files from desktop to android and observe that android receives the files
sequentially using only 1 notification

Send multiple files from an kdeconnect-kde installation and observe that android receives the
files in parallel using multiple notifications

Reviewers: #kde_connect, nicolasfella, albertvaka

Reviewed By: #kde_connect, albertvaka

Subscribers: albertvaka, nicolasfella, kdeconnect

Tags: #kde_connect

Differential Revision: https://phabricator.kde.org/D17627