Restructure lighting queue runnable handling

Instead of overriding add within the queue, never add runnables to the
queue if the light queue is disabled.

This change is made to make timings reports and stacktraces less
confusing for administrators, who prior to this change, would have seen
the lighting queue referenced in both, regardless of whether or not it
was enabled.

This change should not affect performance, nor is it made with the
intent to.

Spigot-Server-Patches/Anti-Xray.patch

@@ -993,7 +993,7 @@ index 00000000..8ea2beb5
 +    }
 +}
 diff --git a/src/main/java/net/minecraft/server/Chunk.java b/src/main/java/net/minecraft/server/Chunk.java
-index e6e54965..33018fa3 100644
+index 1d056031..d1066d82 100644
 --- a/src/main/java/net/minecraft/server/Chunk.java
 +++ b/src/main/java/net/minecraft/server/Chunk.java
 @@ -0,0 +0,0 @@ public class Chunk {
@@ -1477,7 +1477,7 @@ index 48a008e0..045adbd3 100644
                  } else {
                      this.a((Packet) (new PacketPlayOutMultiBlockChange(this.dirtyCount, this.dirtyBlocks, this.chunk)));
 diff --git a/src/main/java/net/minecraft/server/PlayerInteractManager.java b/src/main/java/net/minecraft/server/PlayerInteractManager.java
-index a1689c06..b1826332 100644
+index a49b5c81..5ec7f581 100644
 --- a/src/main/java/net/minecraft/server/PlayerInteractManager.java
 +++ b/src/main/java/net/minecraft/server/PlayerInteractManager.java
 @@ -0,0 +0,0 @@ public class PlayerInteractManager {
@@ -1502,7 +1502,7 @@ index 8860a012..fa0d66d6 100644
          return this.a.size();
      }
 diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
-index f690aaa1..e193f86f 100644
+index 00513d02..592e5b3b 100644
 --- a/src/main/java/net/minecraft/server/World.java
 +++ b/src/main/java/net/minecraft/server/World.java
 @@ -0,0 +0,0 @@ import org.bukkit.generator.ChunkGenerator;