Add unit tests of treeinfo content
Like test_isoinfo.py tests ISO media detection from isoinfo output, we should add unit test detection based on treeinfo content. This will ensure we don't mess up detection for old distros when adding any new regex, which is particularly relevant with fallback/catchall regex annotations.
With this we should add scripts/osinfo-db-add-tree.py for populating initial test content, and filling in content for new distros.