Separate TRACKER_DEBUG from G_ENABLE_DEBUG
We want to enable TRACKER_DEBUG everywhere. Distros ship release builds to users, and when these users report bugs we need to get detailed logging from the build they are using.
Currently this is gated behind Meson buildtype option, which enables G_ENABLE_DEBUG iff buildtype=debug. That is unrelated to logging debug messages and distros can reasonably want to disable this.