Hubcap needs to know about dependencies.yml

[joellabes]

dbt-labs/dbt-core#7631 / dbt-labs/dbt-core#7372 added the ability for package dependencies to be defined in dependencies.yml.

Hubcap needs to know to check that file's packages block as well.

It also needs to enforce the rules/outcomes listed here, especially the rule about only one of packages.yml and dependencies.yml being allowed to contain a packages key. I suspect that will need to be through duplication of logic as opposed to being able to just use dbt-core's logic, which is unfortunate.