Port to Tracker 3
Mostly the port is straightforward, we connect to tracker-miner-fs explicitly over D-Bus instead of the centralized tracker-store daemon we connected to previously.
There are more changes in nautilus-tag-manager.c because the TrackerNotifier API changed, it no longer queries the URIs for us so we need to query these ourselves, and maintain a table of ID->URI mappings in addition to the URI->ID mapping that we already maintained.
Marked WIP as I've done no testing yet, and this also drops support for Tracker 2.0. We hope to do a complete switch to Tracker 3.0 for the GNOME 3.38 release, tracking issue is here: tracker#194 (closed)