[ExtractorCollection] Add unit-test to verify only specific extractor is used
Summary: If there is a direct match, only the matching extractor plugin should be used
Reviewers: Frameworks, astippich
Reviewed By: astippich
Subscribers: kde-frameworks-devel, Baloo
Tags: Frameworks, Baloo
Differential Revision: https://phabricator.kde.org/D16592