Load image with resampling to prevent OOM

Summary:
When loading large images you can run into an OOM situation crashing
the app and leaving the progress notification displayed indefinitely

BUG: 397507

Test Plan:
Before applying the patch find a phone where the app crashes when you send a very large
image to it (my 6.0.1 phone did not even crash when i send it a 85MB image but my 4.0.4 phone
already crashes on a 7MB image)

Apply patch install and send image again

Reviewers: KDE Connect, albertvaka

Reviewed By: KDE Connect, albertvaka

Subscribers: albertvaka, kdeconnect

Tags: KDE Connect

Differential Revision: https://phabricator.kde.org/D16712