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-API-Patches/Add-More-Creeper-API.patch

@@ -6,7 +6,7 @@ Subject: [PATCH] Add More Creeper API
 
 diff --git a/src/main/java/com/destroystokyo/paper/event/entity/CreeperIgniteEvent.java b/src/main/java/com/destroystokyo/paper/event/entity/CreeperIgniteEvent.java
 new file mode 100644
-index 00000000..3d10bb03
+index 000000000..ff10251b6
 --- /dev/null
 +++ b/src/main/java/com/destroystokyo/paper/event/entity/CreeperIgniteEvent.java
 @@ -0,0 +0,0 @@
@@ -16,6 +16,7 @@ index 00000000..3d10bb03
 +import org.bukkit.event.Cancellable;
 +import org.bukkit.event.HandlerList;
 +import org.bukkit.event.entity.EntityEvent;
++import org.jetbrains.annotations.NotNull;
 +
 +/**
 + * Called when a Creeper is ignite flag is changed (armed/disarmed to explode).
@@ -25,11 +26,12 @@ index 00000000..3d10bb03
 +    private boolean canceled;
 +    private boolean ignited;
 +
-+    public CreeperIgniteEvent(Creeper creeper, boolean ignited) {
++    public CreeperIgniteEvent(@NotNull Creeper creeper, boolean ignited) {
 +        super(creeper);
 +        this.ignited = ignited;
 +    }
 +
++    @NotNull
 +    @Override
 +    public Creeper getEntity() {
 +        return (Creeper) entity;
@@ -51,17 +53,19 @@ index 00000000..3d10bb03
 +        canceled = cancel;
 +    }
 +
++    @NotNull
 +    @Override
 +    public HandlerList getHandlers() {
 +        return handlers;
 +    }
 +
++    @NotNull
 +    public static HandlerList getHandlerList() {
 +        return handlers;
 +    }
 +}
 diff --git a/src/main/java/org/bukkit/entity/Creeper.java b/src/main/java/org/bukkit/entity/Creeper.java
-index f957d836..b9877fb8 100644
+index f957d8368..b9877fb88 100644
 --- a/src/main/java/org/bukkit/entity/Creeper.java
 +++ b/src/main/java/org/bukkit/entity/Creeper.java
 @@ -0,0 +0,0 @@ public interface Creeper extends Monster {