Add logic for new free user cap enforcement direction

What does this MR do and why?

• add net new namespace logic to free user cap as we want to treat them differently and restrict them to dashboard_limit from the start
• introduce new feature flag to toggle the net new namespace logic separately from free_user_cap which will affect existing namespaces
• re-organize classes involved to introduce a base concept so that we can be more intentional about functionality between standard and preview

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.

Related to #371915