Updated Upstream (Bukkit/CraftBukkit/Spigot)

Upstream has released updates that appears to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing

Please note that this build includes changes to meet upstreams
requirements for nullability annotations. While we aim for a level of
accuracy, these might not be 100% correct, if there are any issues,
please speak to us on discord, or open an issue on the tracker to
discuss.

Bukkit Changes:
9a6a1de3 Remove nullability annotations from enum constructors
3f0591ea SPIGOT-2540: Add nullability annotations to entire Bukkit API

CraftBukkit Changes:
8d8475fc SPIGOT-4666: Force parameter in HumanEntity#sleep
8b1588e2 Fix ExplosionPrimeEvent#setFire not working with EnderCrystals
39a287b7 Don't ignore newlines in PlayerListHeader/Footer

Spigot Changes:
cf694d87 Add nullability annotations

Spigot-Server-Patches/Allow-setting-the-vex-s-summoner.patch

@@ -5,7 +5,7 @@ Subject: [PATCH] Allow setting the vex's summoner
 
 
 diff --git a/src/main/java/net/minecraft/server/EntityVex.java b/src/main/java/net/minecraft/server/EntityVex.java
-index c3864b86..589b13f4 100644
+index c3864b869..589b13f4e 100644
 --- a/src/main/java/net/minecraft/server/EntityVex.java
 +++ b/src/main/java/net/minecraft/server/EntityVex.java
 @@ -0,0 +0,0 @@ public class EntityVex extends EntityMonster {
@@ -17,7 +17,7 @@ index c3864b86..589b13f4 100644
          this.b = entityinsentient;
      }
 diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftVex.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftVex.java
-index c96a5df8..b09da64c 100644
+index c96a5df80..b09da64c3 100644
 --- a/src/main/java/org/bukkit/craftbukkit/entity/CraftVex.java
 +++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftVex.java
 @@ -0,0 +0,0 @@ public class CraftVex extends CraftMonster implements Vex {