Move existing location system onto chapter model

[dboyer]

In the existing system, location is associated with the ChA. In #4439, we separated out chapter location so that the ChA location is now just their personal location.

We need to add a method for tracking location to the chapter model. For now, let's add the existing location code. This may change in the future if we move toward the bucket system.

[shaun-technovation]

Chapters already have their own location (on the back-end/in the database). When we run the rake task to convert ChAs to chapters, it will copy the ChA's location to the chapter. However there isn't currently a way for admins to edit the location yet, #4685 is for that. I also found #4683, for adding location when chapters are manually added. I think we might be good regarding this issue? 🤔

[dboyer]

Perhaps this issue covers updating the "Location Served by Chapter" field on the ChA dashboard. Right now it pulls in the ChA's location, not the chapter location.

[dboyer]

Location system on chapter model is being used for the chapter selection work happening in #4408. The work to update the "location served by chapter" field on the chapter location tab will happen under a different issue as part of giving ChAs the ability to edit the chapter location.