Random cleanups to users of Level.OVERWORLD and reduce minecraft_server usage (#1697)

- Use `overworld()` instead of `getLevel(Level.OVERWORLD)` when convenient
- Remove now unnecessary `// OW` comments, from when it had no mappings
- Make spawn chunk size and light batches not depend on global server instance
- Merge all spawn chunk size logic into SpawnChunks instead of methods in the validator
- Remove unneeded `withWorld(OVERWORLD)` with just-created server `CommandSource`s
- Use enhanced for in light batch application

src/main/java/carpet/mixins/MinecraftServer_coreMixin.java

@@ -3,9 +3,12 @@ package carpet.mixins;
 import carpet.CarpetServer;
 import carpet.CarpetSettings;
 import carpet.utils.CarpetProfiler;
+import carpet.utils.SpawnChunks;
 import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
 import net.minecraft.server.level.progress.ChunkProgressListener;
 import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
@@ -56,12 +59,15 @@ public abstract class MinecraftServer_coreMixin
         CarpetServer.onServerDoneClosing((MinecraftServer) (Object) this);
     }
 
+    @Shadow
+    public abstract ServerLevel overworld();
+
     @Inject(method = "prepareLevels", at = @At("RETURN"))
     private void afterSpawnCreated(ChunkProgressListener worldGenerationProgressListener, CallbackInfo ci)
     {
         if (CarpetSettings.spawnChunksSize != 11)
-            CarpetSettings.ChangeSpawnChunksValidator.changeSpawnSize(CarpetSettings.spawnChunksSize);
+            SpawnChunks.changeSpawnSize(overworld(), CarpetSettings.spawnChunksSize);
         
-        CarpetSettings.LightBatchValidator.applyLightBatchSizes(CarpetSettings.lightEngineMaxBatchSize);
+        CarpetSettings.LightBatchValidator.applyLightBatchSizes((MinecraftServer) (Object) this, CarpetSettings.lightEngineMaxBatchSize);
     }
 }

src/main/java/carpet/mixins/ServerPlayer_scarpetEventMixin.java

@@ -110,7 +110,7 @@ public abstract class ServerPlayer_scarpetEventMixin extends Player implements S
         {
             ServerPlayer player = (ServerPlayer) (Object)this;
             Vec3 to = null;
-            if (!wonGame || previousDimension != Level.END || destination.dimension() != Level.OVERWORLD) // end ow
+            if (!wonGame || previousDimension != Level.END || destination.dimension() != Level.OVERWORLD)
             {
                 to = position();
             }