Backported Minecarts

-Fixed this mod causing world creation to freeze, especially when the world generated spawns the player close to a mineshaft.

-Fixed the minecart's yaw rotations not rotating correctly in certain conditions and not rotating smoothly in general.

-Fixed minecarts not being able to go down slopes that are not connected to rails, they just get stuck and "bump" against the floor.

-Added minecartMaxSpeed gamerule. Default is 8 just like in 1.21.2. (KNOWN ISSUE: Riding a very fast minecart messes with your camera position! This might be nauseating for some people. At best, I recommend up to speed 48, as that is the most stable speed before this issue appears.)