Improve Structures Checking

Improves performance by keying every chunk thats part of a structure to a hashmap
instead of only the first one.

This allows us to avoid iterating the entire structures value set to see
if a block position is inside of a structure.

This should have pretty decent performance improvement to any standard world
that has been around for a whilewith lots of structures due to ineffeciencies
in how MC stores structures (even unloaded chunks has structured data loaded)

Spigot-Server-Patches/MC-Utils.patch

@@ -25,6 +25,19 @@ index 4bbebb25a..c4d9344a7 100644
      @Nullable
      public TileEntity a(BlockPosition blockposition, Chunk.EnumTileEntityState chunk_enumtileentitystate) {
          // CraftBukkit start
+diff --git a/src/main/java/net/minecraft/server/ChunkCoordIntPair.java b/src/main/java/net/minecraft/server/ChunkCoordIntPair.java
+index 239440888..aafd23beb 100644
+--- a/src/main/java/net/minecraft/server/ChunkCoordIntPair.java
++++ b/src/main/java/net/minecraft/server/ChunkCoordIntPair.java
+@@ -0,0 +0,0 @@ public class ChunkCoordIntPair {
+         this.z = blockposition.getZ() >> 4;
+     }
+ 
++    public static long asLong(final BlockPosition pos) { return a(pos.getX() >> 4, pos.getZ() >> 4); } // Paper - OBFHELPER
++    public static long asLong(int x, int z) { return a(x, z); } // Paper - OBFHELPER
+     public static long a(int i, int j) {
+         return (long) i & 4294967295L | ((long) j & 4294967295L) << 32;
+     }
 diff --git a/src/main/java/net/minecraft/server/DataPaletteBlock.java b/src/main/java/net/minecraft/server/DataPaletteBlock.java
 index 1f2fe87b6..2cb462b8e 100644
 --- a/src/main/java/net/minecraft/server/DataPaletteBlock.java