Less strict requirements for transports loading units

Currently, to load a unit a transport needs to rotate its orientation to the match the unit being loaded. It also requires the unit to be within a fixed maximum radius. These can lead to poor gameplay experiences, as transports picking up units can be slow and finicky, rather than It Just Works™.

Allow games to configure the loading radius, as well as being able to load units at any angle. The desire in BAR is that the unit being loaded is translated and rotated into position in the transport, rather than the transport having to align itself with the unit being loaded.

No files or tests are named. Start by tracing the transport unit-loading logic and the existing fixed loading-radius and orientation checks; done should include configurable radius handling and loading that translates and rotates the unit into the transport without requiring transport alignment.

Written by the indexing model from the issue text.