This change doesn't make much sense now, as projects are read-only
anyways, so there's not a lot that importing really does for you--you
can already reference pre-existing projects just by defining them in
your config.
But as we discussed #10425, this change made more and more sense. In a
world where projects can be created, we can no longer reference
pre-existing projects just by defining them in config. We get that
ability back by making projects importable.
