Preserve rotation on teleport command and add PlayerChangedWorldEvent for teleportAsync

[luigiofthebakery]

When using the teleport command, rotation (pitch and yaw) was not preserved when teleporting to an entity, or in any situation where it wasn't explicitly specified in the command parameters. The first commit fixes that. The second commit adds back PlayerChangedWorldEvent to fire after teleportAsync is called, if the entity is a player and they are teleporting to a new world.