Make WorldCreator#keepSpawnLoaded return the WorldCreator (Fixes #8321) (#8371)

* Make WorldCreator#keepSpawnLoaded return the WorldCreator (Fixes #8321)

Thought that I fixed this before push/merge, apparently not, hence, fix
the return type and add mitigation for this.

* Fix patch/build

* Rebuild patches

patches/api/0378-WorldCreator-keepSpawnLoaded.patch

@@ -5,7 +5,7 @@ Subject: [PATCH] WorldCreator#keepSpawnLoaded
 
 
 diff --git a/src/main/java/org/bukkit/WorldCreator.java b/src/main/java/org/bukkit/WorldCreator.java
-index cbdcac688afb7c13dd7058fa522bbd2c5adc445e..355f9f27d29c65efebf099a72c37892a309edef1 100644
+index cbdcac688afb7c13dd7058fa522bbd2c5adc445e..dc92ce261b9e67979da3f82cb75292ff980ad87e 100644
 --- a/src/main/java/org/bukkit/WorldCreator.java
 +++ b/src/main/java/org/bukkit/WorldCreator.java
 @@ -22,6 +22,7 @@ public class WorldCreator {
@@ -16,7 +16,7 @@ index cbdcac688afb7c13dd7058fa522bbd2c5adc445e..355f9f27d29c65efebf099a72c37892a
  
      /**
       * Creates an empty WorldCreationOptions for the given world name
-@@ -573,4 +574,29 @@ public class WorldCreator {
+@@ -573,4 +574,32 @@ public class WorldCreator {
  
          return result;
      }
@@ -38,10 +38,13 @@ index cbdcac688afb7c13dd7058fa522bbd2c5adc445e..355f9f27d29c65efebf099a72c37892a
 +     * configuration, otherwise, will act as an override towards this setting
 +     *
 +     * @param keepSpawnLoaded the new value
++     * @return This object, for chaining
 +     */
-+    public void keepSpawnLoaded(@NotNull net.kyori.adventure.util.TriState keepSpawnLoaded) {
++    @NotNull
++    public WorldCreator keepSpawnLoaded(@NotNull net.kyori.adventure.util.TriState keepSpawnLoaded) {
 +        java.util.Objects.requireNonNull(keepSpawnLoaded, "keepSpawnLoaded");
 +        this.keepSpawnLoaded = keepSpawnLoaded;
++        return this;
 +    }
 +
 +    // Paper end

patches/server/0945-Mitigate-effects-of-WorldCreator-keepSpawnLoaded-ret.patch

@@ -0,0 +1,25 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Shane Freeder <theboyetronic@gmail.com>
+Date: Mon, 19 Sep 2022 00:13:02 +0100
+Subject: [PATCH] Mitigate effects of WorldCreator#keepSpawnLoaded ret type
+ change
+
+TODO: Remove in 1.21?
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/util/Commodore.java b/src/main/java/org/bukkit/craftbukkit/util/Commodore.java
+index 27646d963bd1158f3fe0a9c0593a312404f0e7b0..128113e64731be9c0a4008ffb0a1eae78e221c47 100644
+--- a/src/main/java/org/bukkit/craftbukkit/util/Commodore.java
++++ b/src/main/java/org/bukkit/craftbukkit/util/Commodore.java
+@@ -434,6 +434,12 @@ public class Commodore
+                         {
+                             desc = getOriginalOrRewrite(desc);
+                         }
++                        if (owner.equals("org/bukkit/WorldCreator") && name.equals("keepSpawnLoaded") && desc.equals("(Lnet/kyori/adventure/util/TriState;)V")) {
++                            super.visitMethodInsn(opcode, owner, name, "(Lnet/kyori/adventure/util/TriState;)Lorg/bukkit/WorldCreator;", itf);
++                            // new method has a return, so, make sure we pop it
++                            super.visitInsn(Opcodes.POP);
++                            return;
++                        }
+                         // Paper end
+ 
+                         if ( modern )