feat: Refactor Dispatched Action db entity to use full-fat Activity

[FoxxMD]

• Instead of storing limited info about an Activity in the table just persist the full Activity with a relationship
• Fixes issue on CM init where snoowrap needs to fetch all activities for dispatched actions in order to get permalinks and simplifies things in general

[FoxxMD]

This seems to work, at least in simple cases, but I found it was not finding all associated Activities correctly when used in real-world. There was also an issue with re-hydrating activities for some reason.

I think the issue stems from using entity manager methods instead of full-fat query builder methods. The EM stuff has always been inconsistent in behavior -- previously experienced it not hydrating thing correctly when implementing Actioned Events selector.

Need to refactor EM usage into explicit query builder which I think will solve this.