D8776: [autotests] Add tests for DRM platform plugin

[Martin Flöser]

graesslin added a dependency: D8752: [platforms/drm] At safety checks for the 
properties.

REVISION DETAIL
  https://phabricator.kde.org/D8776

To: graesslin, #kwin, #plasma
Cc: plasma-devel, ZrenBot, progwolff, lesliezhai, ali-mohamed, jensreuterberg, 
abetts, sebas, apol, mart