Update last chunk position in findSupportingBlock

Fixes fetching chunks needlessly multiple times.

Thanks Lulu13022002 for pointing this out

patches/server/Moonrise-optimisation-patches.patch

@@ -31694,6 +31694,8 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +                final int newChunkZ = currZ >> 4;
 +
 +                if (((newChunkX ^ lastChunkX) | (newChunkZ ^ lastChunkZ)) != 0) {
++                    lastChunkX = newChunkX;
++                    lastChunkZ = newChunkZ;
 +                    lastChunk = (LevelChunk)chunkSource.getChunk(newChunkX, newChunkZ, ChunkStatus.FULL, false);
 +                }
 +