Follows rP25071 (Motion Manager), which broke it again. Also follows pushing, which changes some assumptions to be made.
References / reverts parts of rP24798 / rP24800.
Because the motion manager made things symmetrical, we can remove the Fleeing hack, & we don't have to check the order in which movement is computed (which is a good thing because it's know undetermined).
The pushing diff requires a few tweaks, but this passes the map tests, which proved to be quite extensive & arguably simplifies code.