Updates an area using the specified #GraphUpdateObject.
Notes to implementators. This function should (in order):
Call o.WillUpdateNode on the GUO for every node it will update, it is important that this is called BEFORE any changes are made to the nodes.
Update walkabilty using special settings such as the usePhysics flag used with the GridGraph.
Call Apply on the GUO for every node which should be updated with the GUO.
Update connectivity info if appropriate (GridGraphs updates connectivity, but most other graphs don't since then the connectivity cannot be recovered later).
UpdateAreaInit
(o)
May be called on the Unity thread before starting the update.
May be called on the Unity thread before starting the update.
May return a GraphUpdatePromise or null. If a GraphUpdatePromise is returned it will be polled on the main thread until it returns done. Only then will it progress to the next stage. The `Complete` method may be called if the graph update needs to be completed immediately.