Read entries from packages_composer_packages table

In Foundation: Prepare application code to read fr... (#548761) we've changed the application code to make it's possible to read the entries from a detached table using a specific package class.

In Rename composer package class (!195745 - merged) we've renamed the existing model for composer packages from Packages::Composer::Package to Packages::Composer::Sti::Package. This'll allow us to use Packages::Composer::Package to read the entries from packages_composer_packages column.

There're several parts that should be changed:

• Composer client API
• REST API
• GraphQL API