Rework layer config

[MelanX]

Describe your idea

Add a way to randomly generate some other blocks in each layer, but still keep the way current way to do it. Now:

"minecraft:overworld": "minecraft:bedrock,63*minecraft:blackstone,319*minecraft:stone,minecraft:bedrock"

Then, same output:

"minecraft:overworld": [
  {
    "block": "minecraft:bedrock"
  },
  {
    "amount": 63,
    "block": "minecraft:blackstone"
  },
  {
    "amount": 319,
    "block": "minecraft:stone"
  },
  {
    "block": "minecraft:bedrock"
  }
]

Similar, but layer 65-69 will have 30% chance to generate infested stone or cobblestone, chosen by weight:

"minecraft:overworld": [
  {
    "block": "minecraft:bedrock"
  },
  {
    "amount": 63,
    "block": "minecraft:blackstone"
  },
  {
    "amount": 5,
    "block": "minecraft:stone",
    "extras": {
      "chance": 0.3,
      "blocks": [
        {
          "block": "minecraft:infested_stone",
          "weight": 9
        },
        {
          "block": "minecraft:cobblestone"
        }
      ]
    }
  },
  {
    "amount": 314,
    "block": "minecraft:stone"
  },
  {
    "block": "minecraft:bedrock"
  }
]