SPIGOT-4137: Fix World.regenerateChunk

By: md_5 <git@md-5.net>

paper-server/nms-patches/ChunkTaskScheduler.patch

@@ -0,0 +1,15 @@
+--- a/net/minecraft/server/ChunkTaskScheduler.java
++++ b/net/minecraft/server/ChunkTaskScheduler.java
+@@ -39,6 +39,12 @@
+         this.f = iasynctaskhandler;
+     }
+ 
++    // CraftBukkit start
++    public void forcePolluteCache(ChunkCoordIntPair chunkcoordintpair) {
++        this.g.put(chunkcoordintpair.a(), new Scheduler.a(chunkcoordintpair, new ProtoChunk(chunkcoordintpair, ChunkConverter.a), ChunkStatus.EMPTY));
++    }
++    // CraftBukkit end
++
+     protected Scheduler.a a(ChunkCoordIntPair chunkcoordintpair) {
+         return (Scheduler.a) this.g.computeIfAbsent(Long.valueOf(chunkcoordintpair.a()), (olong) -> {
+             ProtoChunk protochunk = this.a(chunkcoordintpair.x, chunkcoordintpair.z);