This doesn't require `ql.name` and is simpler while we don't have
to write upgrade scripts. The `ql.name` mechanism might get useful
once we do have to write upgrade scripts, as that doesn't change the
dbscheme.
We've been observing some performance issues using crate_universe on CI.
Therefore, we're moving to vendor the auto-generated BUILD files
in our repository. This should provide a nice speed boost, while
getting rid of the complexity of the "rust cache" job we've been using
when we had a lot of git dependencies.
This PR includes a vendor script, and I'll put up a CI job internally
that runs that vendor script on Cargo.toml and Cargo.lock changes, to check
that the vendored files are in sync.
