Changes to map.cs, rename IPositionable.IsLeaving{ => Cell}, add IPositionable.GetValidSubCell
Sub-cell aware co-path-finding with dynamic range

Continued changes from #6208 to IMove.
Removed non-sub-cell ctors from Move
Enhanced path-finder
	Mid-distance ranging to get closer when actor is already in range
	Sub-cell aware co-path-finding - tries to use the same path for actors from the same cell
	Forward adjacent co-path-finding - tries to use a cached path from a forward adjacent cell
	Actor type specific near enough ranges - long range & explosive actors can spread out more & stay further back