Don't create nether/end islands until player goes to that dimension

[DuneSciFye]

Rather than making a nether/end island/world when the player creates an island, make it when the player goes through a nether or end portal.

This would save up resources all around, as there would be less islands/worlds to load most of the time, and storage would be reduce.

This would be applicable to the majority of servers, as end islands generally wouldn't be accessible from the getgo, if end islands are accessible at all. And if you do this to end islands, might as well do it for nether islands as well.

For people using SlimeWorldManager (such as myself), it is extremely crucial, reducing the number of worlds loaded generally by two thirds, which greatly improved performance.

[DuneSciFye]

Seems that when you make the island, it only creates the normal world, but when joining the server again, it creates the other two worlds.