Reuse cave biome cache

- Carve scratch keeps one cave biome cache per thread, cleared per chunk

core/src/main/java/art/arcane/iris/generation/stage/IrisCarveModifier.java

@@ -102,9 +102,9 @@ public class IrisCarveModifier extends EngineAssignedModifier<NativeBlockState>
         PrecisionStopwatch caveStopwatch = PrecisionStopwatch.start();
         Mantle<Matter> mantle = getEngine().getMantle().getMantle();
         CaveInputs resolverState = new CaveInputs(getEngine());
-        Long2ObjectOpenHashMap<IrisBiome> caveBiomeCache = new Long2ObjectOpenHashMap<>(2048);
         IrisCarveScratch scratch = SCRATCH.get();
         scratch.reset();
+        Long2ObjectOpenHashMap<IrisBiome> caveBiomeCache = scratch.caveBiomeCache;
         CarveWallBuffer walls = scratch.walls;
         CarveColumnMask[] columnMasks = scratch.columnMasks;
         CarveColumnMask[] boundaryMasks = scratch.boundaryMasks;

core/src/main/java/art/arcane/iris/generation/stage/IrisCarveScratch.java

@@ -21,6 +21,7 @@ package art.arcane.iris.generation.stage;
 import art.arcane.iris.generation.biome.IrisBiome;
 import art.arcane.volmlib.util.matter.MatterCavern;
 import art.arcane.volmlib.util.math.PowerOfTwoCoordinates;
+import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
 
 import java.util.Arrays;
 import java.util.HashMap;
@@ -32,6 +33,7 @@ final class IrisCarveScratch {
     final int[] surfaceHeights = new int[256];
     final CarveWallBuffer walls = new CarveWallBuffer(512);
     final Map<String, IrisBiome> customBiomeCache = new HashMap<>();
+    final Long2ObjectOpenHashMap<IrisBiome> caveBiomeCache = new Long2ObjectOpenHashMap<>(4096);
     int[] upperSurfaceHeights;
     boolean customCaveBiomePresent;
 
@@ -56,6 +58,7 @@ final class IrisCarveScratch {
         }
         walls.clear();
         customBiomeCache.clear();
+        caveBiomeCache.clear();
         customCaveBiomePresent = false;
     }
 }