LIKA-593: Only show subsystems with a description and services on front page

[bzar]

Description

Front page featured subsystems should contain only subsystems with a description and at least one service

Jira ticket reference: LIKA-593

What has changed:

• Added sort parameter to package_generator, defaults to default sorting
• Modified get_homepage_datasets to filter the results based on criteria
  • The implementation fetches candidates in a paged fashion to reduce the likely amount of data fetched each front page load

Checklist

• Contains schema changes.
• Schema changes require migration of existing data.
• Contains migration script for existing data.
• Changes should be covered by tests.
• Changes are covered by tests.

Does this have a design impact ?

• Yes
• No

Add screenshots of design changes here if yes.