add simple test rig for service runner

Summary:

• make sure that chrome apps have lower relevance than chrome itself
• makes sure that konsole has higher relevance than yakuake (latter only references onsole in the comment entry)

Test Plan:

• it passes and at a glance doesn't seem to break my production sycoca

Would be cool if @dfaure could take a look at the ksycoca setup to make sure the test doesn't negatively impact the production cache.

Reviewers: broulik, dfaure

Reviewed By: dfaure

Subscribers: dfaure, plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D3707