Display star ratings

Summary:
For quite some time, users and reviewers have been asking for Discover to display star ratings. This is really useful information, and becomes especially important now that we have multiple sort modes. People will think, "this list may be sorted by rating, but what ARE the ratings?"

This patch adds star ratings to the browse and search lists, and the detailed view pages.

It also adjusts the look of the delegates to better accommodate stars without becoming cluttered.

FEATURE: 389601
FIXED-IN: 5.13.0

Depends on D11842, because we need the extra space gained by removing the less-useful categories.

Test Plan:
Before:

After, Applications page:

After, Installed page:

After, Applications Page in compact or mobile view:

Reviewers: apol, Discover Software Store, VDG

Reviewed By: apol, Discover Software Store

Subscribers: abetts, rkflx, fabianr, ragreen, acrouthamel, plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D11876