appstreamrunner: Port to KApplicationTrader

Summary:
Port away from the query language to lambda using the new KApplicationTrader API.

Depends on D27953.

Test Plan: Tested by hand with several applications, still works as expected.

Reviewers: Plasma, dfaure

Reviewed By: dfaure

Subscribers: plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D27954