allow vr / ar users to change anchor change location

[kfarr]

as a user I can change the anchor location

with vr or hand controls:

• my controller or hand can collide with a square that is roughly the size of city hall, perhaps a bit larger
• i can press any button (or pinch) while colliding, hold it down (or keep pinching), and move the town hall and also the entire grid of my city (this could be a geometry on the same as the anchor city-container entity)
• it will also attempt to replace the anchor, ideally a persistent spatial anchor
• bonus: add in-vr messages to notify component and use it to confirm anchor updates (or failures) for debugging