Increase number of Apps you can see at once in list views

Summary:
This patch increases the number of apps that you can see at once in Discover's list views by doing the following:

• Remove long description and only show caption/short description
• Slightly reduce icon size
• Re-arrange things to make everything a bit more compact

Test Plan:
Tested in KDE Neon. Here's a video:

Reviewers: apol, Discover Software Store

Reviewed By: apol, Discover Software Store

Subscribers: colomar, plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D9833