Show+Hide architecture update

[thiessenp-cds]

Update the show+hide architecture to be more performant and maintainable. The motivation for this work is from this support ticket.

Some requirements ideally:

• event-driven approach
• separates concerns cleanly and makes the visibility logic testable in isolation
• visibility logic has unit tests or at least the newly added/touched code does

[anikbrazeau]

https://gcdigital.slack.com/archives/C01GFD150MC/p1783947320443889