Add an admin action to remove orphaned tags

[guel-codes]

Overview

We have a management command to remove orphaned tags but I also wanted to add functionality to do it as an admin action from the drop down list.

Preview

• https://www.loom.com/share/3cd37182c652493997bbfd92f3eab5f9?sid=78dc947a-102c-4f53-800e-368264ac039f

[rtpg]

Alright, tweaked this one up to have an orphaned queryset method, and so that the orphan cleanup only happens within the selected tags (matching the principle that actions occur only among the selected data, it's two clicks to select everything)