Skip quiet block update checks

- ChunkBlockUpdateListener remembers the last state with no update or custom effect
- Plain terrain runs skip the per-block isUpdatable and isCustom checks
- Test replays random writes against the per-write catch semantics

core/src/test/java/art/arcane/iris/generation/runtime/ChunkBlockUpdateListenerTest.java

@@ -0,0 +1,60 @@
+package art.arcane.iris.generation.runtime;
+
+import art.arcane.volmlib.nativelib.terrain.NativeBlockState;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class ChunkBlockUpdateListenerTest {
+    @Test
+    public void forwardsExactlyTheWritesWithBlockUpdateEffects() {
+        NativeBlockState stone = state(false, false);
+        NativeBlockState deepslate = state(false, false);
+        NativeBlockState water = state(true, false);
+        NativeBlockState custom = state(false, true);
+        NativeBlockState[] palette = {stone, deepslate, water, custom, null};
+        Random random = new Random(42L);
+        List<String> expected = new ArrayList<>();
+        List<String> actual = new ArrayList<>();
+        BlockUpdater reference = effects(expected);
+        ChunkBlockUpdateListener listener = new ChunkBlockUpdateListener(effects(actual), 160, -48);
+
+        for (int write = 0; write < 20_000; write++) {
+            NativeBlockState state = palette[random.nextInt(8) < 5 ? random.nextInt(2) : random.nextInt(palette.length)];
+            int x = random.nextInt(16);
+            int y = random.nextInt(384);
+            int z = random.nextInt(16);
+            reference.catchBlockUpdates(160 + x, y, -48 + z, state);
+            listener.onWrite(x, y, z, state);
+        }
+
+        assertEquals(expected, actual);
+    }
+
+    private static BlockUpdater effects(List<String> log) {
+        return (x, y, z, data) -> {
+            if (data == null) {
+                return;
+            }
+            if (data.isUpdatable()) {
+                log.add("update " + x + "," + y + "," + z);
+            }
+            if (data.isCustom()) {
+                log.add("custom " + (x >> 4) + "," + (z >> 4));
+            }
+        };
+    }
+
+    private static NativeBlockState state(boolean updatable, boolean custom) {
+        NativeBlockState state = mock(NativeBlockState.class);
+        when(state.isUpdatable()).thenReturn(updatable);
+        when(state.isCustom()).thenReturn(custom);
+        return state;
+    }
+}