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/ExperienceOrbMergeEvent.patch

@@ -9,7 +9,7 @@ metadata such as spawn reason, or conditionally move data from source to target.
 
 diff --git a/src/main/java/com/destroystokyo/paper/event/entity/ExperienceOrbMergeEvent.java b/src/main/java/com/destroystokyo/paper/event/entity/ExperienceOrbMergeEvent.java
 new file mode 100644
-index 00000000..fb5b4b86
+index 000000000..0ce3e3977
 --- /dev/null
 +++ b/src/main/java/com/destroystokyo/paper/event/entity/ExperienceOrbMergeEvent.java
 @@ -0,0 +0,0 @@
@@ -42,15 +42,16 @@ index 00000000..fb5b4b86
 +import org.bukkit.event.Cancellable;
 +import org.bukkit.event.HandlerList;
 +import org.bukkit.event.entity.EntityEvent;
++import org.jetbrains.annotations.NotNull;
 +
 +/**
 + * Fired anytime the server is about to merge 2 experience orbs into one
 + */
 +public class ExperienceOrbMergeEvent extends EntityEvent implements Cancellable {
-+    private final ExperienceOrb mergeTarget;
-+    private final ExperienceOrb mergeSource;
++    @NotNull private final ExperienceOrb mergeTarget;
++    @NotNull private final ExperienceOrb mergeSource;
 +
-+    public ExperienceOrbMergeEvent(ExperienceOrb mergeTarget, ExperienceOrb mergeSource) {
++    public ExperienceOrbMergeEvent(@NotNull ExperienceOrb mergeTarget, @NotNull ExperienceOrb mergeSource) {
 +        super(mergeTarget);
 +        this.mergeTarget = mergeTarget;
 +        this.mergeSource = mergeSource;
@@ -59,6 +60,7 @@ index 00000000..fb5b4b86
 +    /**
 +     * @return The orb that will absorb the other experience orb
 +     */
++    @NotNull
 +    public ExperienceOrb getMergeTarget() {
 +        return mergeTarget;
 +    }
@@ -66,16 +68,19 @@ index 00000000..fb5b4b86
 +    /**
 +     * @return The orb that is subject to being removed and merged into the target orb
 +     */
++    @NotNull
 +    public ExperienceOrb getMergeSource() {
 +        return mergeSource;
 +    }
 +
 +    private static final HandlerList handlers = new HandlerList();
 +
++    @NotNull
 +    public HandlerList getHandlers() {
 +        return handlers;
 +    }
 +
++    @NotNull
 +    public static HandlerList getHandlerList() {
 +        return handlers;
 +    }