Add basic test functionality

Add a TestJob and associated action in Part. Test functionality is
enabled in plugin json files, currently for clizip, clirar and cli7z.
Test results are displayed simply as success/failure in a KMessageBox.

Testing password-protected archives will currently result in an
errorbox, due to these archives potentially having different passwords
for each file and hence multiple password prompts might pop up.

Libarchive does not support testing archives.

FEATURE: 140492
FIXED-IN: 16.08.0
Differential Revision: D1516