* Add MapSystem.GetMapOrInvalid
This is effectively the same exact behavior as IMapManager.GetMapEntityId. Adding this so I don't have to consider whether warning fixes using MapSystem.GetMap() instead would change behavior.
* Warning fixes around IMapManager.GetMapEntityId
* Fix tests
It would bail out of the entire update logic if you aren't hovering over a map position, which isn't great when the control displays far more than in-simulation mouse position info.