Migrate from product_group to feature_category

What does this MR do and why?

In order to support feature_category, this is to update most instances of product_group within the gitlab_quality-test_tooling gem to support feature_category. The existing DRI assignment can still use product_group for now until we consider taking up gitlab-org/quality&154 for feature team assignment

Relates to gitlab-org/quality/quality-engineering/team-tasks#3834

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.