Add compute_density_function to replace removed `sample_noise (#1591)

src/main/java/carpet/fakes/RandomStateVisitorAccessor.java

@@ -0,0 +1,7 @@
+package carpet.fakes;
+
+import net.minecraft.world.level.levelgen.DensityFunction;
+
+public interface RandomStateVisitorAccessor {
+    DensityFunction.Visitor getVisitor();
+}