Jamie Tanna authored Jan 16, 2024 and Jamie Tanna committed Jan 16, 2024

Similar to the `policy_violations` table, this introduces a single view
of all Advisories data that affects the dependencies in the database.

This makes it simpler to query all package advisories by "simply"
querying the `advisories` table, which includes all relevant information
for package advisories.

This allows us to remove a lot of duplication in our SQL queries for
looking up advisories data, making sure that it's a much simpler process
for querying data.

We can still directly query the tables as before - following the example
from `RetrievePackageAdvisoriesFromSeparateTables` - if we need to.

We can also remove the references in `policy_violations` that indicates
that `policy_violations` is better than `advisories`, as it no longer
is!

Because we want to make it easier to surface the `eol_from` and
`supported_until` dates, too, we should add them as nullable fields to
`advisories` - and defaulting it as `NULL` for tables that don't surface
the data.

Closes #414.