refactor: extract common logic for env feature flags

What does this MR do?

We often use the same logic for feature flags defined in the environment variable. I want to unify this logic and have all the feature flag defined in the same place.

This is the just a first iteration, we can improve on it later.

TODO

• I added the Changelog trailer (e.g. Changelog: feature) to the commits that need to be included in the changelog
• I added unit tests or they are not required
• I added acceptance tests or they are not required
• I added documentation (or it's not required)
• I followed code review guidelines
• I followed Go Style guidelines