Move objects even when sticky blocks are involved

[TurkeyMcMac]

Fixes https://github.com/minetest-mods/mesecons/issues/596. Fixes https://github.com/minetest-mods/mesecons/issues/462.

This significantly complicates the code. I had to add some special cases to replicate the old behavior. For example, when a sticky piston retracts while pulling no blocks, only objects touching the face of the piston head should be pulled. I could simplify the code if this behavior does not need preservation. One thing that did change in the pulling of objects is that mvps no longer pull objects downwards. I think the new behavior is more consistent with the lack of pulling in other directions, although it could affect elevators a bit.

Objects are still dragged on the sides of moving stacks, but no longer are dragged into solid nodes.