[Bleeding] Completely fix the tree generation algorithm to make it near identical to vanilla as well as fix potential bugs associated with disappearing saplings.

src/main/java/net/minecraft/server/WorldGenTrees.java

@@ -4,7 +4,7 @@ import java.util.Random;
 
 import org.bukkit.BlockChangeDelegate; // CraftBukkit
 
-public class WorldGenTrees extends WorldGenerator {
+public class WorldGenTrees extends WorldGenerator implements BlockSapling.TreeGenerator { // CraftBukkit add interface
 
     private final int a;
     private final boolean b;