appmap.yml files, which are located in a project, are indexed.
The .appmap.json files located in the referenced appmap_dir directories are indexed automatically,
as long as these folders are not excluded.
In the IDE, excluded folders prevent indexing of any data.
Therefore, we implement AppMapIndexedRootsSetContributor to prevent this.
This class searches for appmap.yml files in the content roots of a project.
Values appmap_dir of these files are marked to be indexed even when such directory is excluded.
Content roots are usually the top-level directories of a project.
Therefore, appmap.yml files located in a nested, excluded folder won't be found by this implementation.
We're not collecting such files because iterating the complete directory tree is expensive without an index.