As a start towards making SBOMs a first-class datasource, we can
integrate our `advisories` table with Custom Advisories functionality
into the data.

Unfortunately this leads to a lot of "column name is ambiguous" errors,
so we need to introduce table aliases to avoid clashing.

As `Version` can now be nullable, at least in `sboms`, (even though
we've specified `IS NOT NULL`[0]) we need to make sure we handle it,
excluding any empty version numbers.

[0]: https://github.com/sqlc-dev/sqlc/issues/2723