Port add_installed() vfunc to new threading model

See the individual commits for details. As with the previous work to replace the refine() vfunc with GsPluginJobRefine, this replaces add_installed() with GsPluginJobListInstalledApps. It’s a little more straightforward than refine since less of GsPluginLoader is tied up in its implementation.

Signed-off-by: Philip Withnall pwithnall@endlessos.org

Helps: #1472

Merge request reports