Add SDF cluster SDFs

[IntegratedQuantum]

fixes #2751

Example:

		.{
			.id = "cubyz:cluster",
			.minAmount = 0.01,
			.maxAmount = 0.02,
			.smoothness = 4,
			.mode = .additive,
			.children = .{
				.{
					.id = "cubyz:cylinder",
					.minRadius = 8,
					.maxRadius = 8,
					.minHeight = 100,
					.maxheight = 100,
					.positionOffset = .{-30, 0, 0},
				},
				.{
					.id = "cubyz:cylinder",
					.minRadius = 8,
					.maxRadius = 8,
					.minHeight = 100,
					.maxheight = 100,
					.positionOffset = .{30, 0, 0},
				},
				.{
					.id = "cubyz:rectangular_cuboid",
					.minSideLengths = .{80, 35, 100},
					.maxSideLengths = .{80, 35, 100},
					.positionOffset = .{0, 0, 100},
				},
				.{
					.id = "cubyz:rectangular_cuboid",
					.minSideLengths = .{60, 60, 35},
					.maxSideLengths = .{60, 60, 35},
					.positionOffset = .{0, 0, 190},
				},
				.{
					.id = "cubyz:cylinder",
					.minRadius = 8,
					.maxRadius = 8,
					.minHeight = 20,
					.maxheight = 20,
					.positionOffset = .{0, 0, 160},
				},
				.{
					.id = "cubyz:rectangular_cuboid",
					.minSideLengths = .{110, 40, 16},
					.maxSideLengths = .{110, 40, 16},
					.positionOffset = .{0, 0, 142},
				},
				.{
					.id = "cubyz:cylinder",
					.minRadius = 6,
					.maxRadius = 6,
					.minHeight = 80,
					.maxheight = 80,
					.positionOffset = .{65, 0, 110},
				},
				.{
					.id = "cubyz:cylinder",
					.minRadius = 6,
					.maxRadius = 6,
					.minHeight = 80,
					.maxheight = 80,
					.positionOffset = .{-65, 0, 110},
				},
				.{
					.id = "cubyz:cylinder",
					.minRadius = 4,
					.maxRadius = 4,
					.minHeight = 40,
					.maxheight = 40,
					.positionOffset = .{-20, -5, 230},
				},
				.{
					.id = "cubyz:cylinder",
					.minRadius = 4,
					.maxRadius = 4,
					.minHeight = 40,
					.maxheight = 40,
					.positionOffset = .{20, -5, 230},
				},
				.{
					.id = "cubyz:sphere",
					.minRadius = 6,
					.maxRadius = 6,
					.positionOffset = .{-20, -5, 250},
				},
				.{
					.id = "cubyz:sphere",
					.minRadius = 6,
					.maxRadius = 6,
					.positionOffset = .{20, -5, 250},
				},
			},
		},

[Argmaster]

Can we get that sample biome as a rare sky islands biome?

Is it possible to guarantee that those volumes don't overlap?

[IntegratedQuantum]

I think it's a bit too random to put it in the game. I'd rather wait until #2592 and put it rarely in some surface biome.

and no we cannot guarantee that they don't overlap.

[Argmaster]

I was thinking we could make some more of them; I guess a one that just stands doesn't fit in sky islands, but like one with wings in superman flight pose would be cool fit there!