Switch to using ForgeFlower for Paper Only mc-dev imports

ForgeFlower is better than Spigots FernFlower at decompiling the source.

However, in order to maintain the CraftBukkit patches, we must keep
using spigots for the primary.

However, for any file that we import on top of Spigots imported files
there is nothing stopping us from using better decompiled files.

So these changes will use ForgeFlower to maintain a better set of
decomped files, so anything we add on top of Paper can start off
in a better spot.

Spigot-Server-Patches/Prevent-Pathfinding-out-of-World-Border.patch

@@ -6,7 +6,7 @@ Subject: [PATCH] Prevent Pathfinding out of World Border
 This prevents Entities from trying to run outside of the World Border
 
 diff --git a/src/main/java/net/minecraft/server/NavigationAbstract.java b/src/main/java/net/minecraft/server/NavigationAbstract.java
-index 76d1f4bd21..76b2787bae 100644
+index a8b070ed32..452da80f11 100644
 --- a/src/main/java/net/minecraft/server/NavigationAbstract.java
 +++ b/src/main/java/net/minecraft/server/NavigationAbstract.java
 @@ -0,0 +0,0 @@ public abstract class NavigationAbstract {
@@ -22,9 +22,9 @@ index 76d1f4bd21..76b2787bae 100644
          } else {
              BlockPosition blockposition = new BlockPosition(entity);
 +            if (!getEntity().getWorld().getWorldBorder().isInBounds(blockposition)) return null; // Paper - don't path out of world border
- 
              if (this.c != null && !this.c.b() && blockposition.equals(this.q)) {
                  return this.c;
+             } else {
 diff --git a/src/main/java/net/minecraft/server/WorldBorder.java b/src/main/java/net/minecraft/server/WorldBorder.java
 index acd76e13bb..1a87480f09 100644
 --- a/src/main/java/net/minecraft/server/WorldBorder.java