Pods 2.5 optimizations work

This is a general PR for all the 2.x-optimizations work done so far by @jamesgol / @pglewis; to ensure we can see a full big picture of the changes. This will make it easier to review everything as it currently is (or becomes) and I can comment on the difference lines.
The intention of this use was as an action. But yeah, every action is a filter, every filter is an action. But filters must always return something, where as actions don't. If you run an action on a filter, and don't return something, it will break the filtered value returned. In our use case here, we're not using it as a filter, so it won't break anything if you add_filter or add_action, but I'd prefer our usage reflect do_action instead for WP standards.