Updated Upstream (Bukkit/CraftBukkit)

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

Bukkit Changes:
304e83eb PR-1002: Improve documentation and implementation of getMaxStackSize
e8215ea2 SPIGOT-7638: Library loader does not seem to resolve every dependency
79c595c0 SPIGOT-7637: Bad logic in checking nullability of AttributeModifier slots

CraftBukkit Changes:
91b1fc3f1 SPIGOT-7644: Fix ItemMeta#getAsString
4e77a81e1 SPIGOT-7615: PlayerLeashEntityEvent cancelled eats lead
996f660f3 Do not remove leash knot if leasing to an existing leash knot gets cancelled
f70367d42 SPIGOT-7643: Fix inverted leash event cancelled usage and remove leash knot if no entity gets leashed
7ddb48294 SPIGOT-7640: Abnormal jumping height of wind charge
080c8711e SPIGOT-7639: Incoming plugin channels not working
ad549847e Open a direct connection instead of pinging mojang server to check if it is reachable
38e2926c5 SPIGOT-7365: DamageCause blocked by shield should trigger invulnerableTime

patches/server/0245-Add-ray-tracing-methods-to-LivingEntity.patch

@@ -5,10 +5,10 @@ Subject: [PATCH] Add ray tracing methods to LivingEntity
 
 
 diff --git a/src/main/java/net/minecraft/world/entity/LivingEntity.java b/src/main/java/net/minecraft/world/entity/LivingEntity.java
-index 7d44d4563e39f279cf335f307a4d84d0758858ee..67ba23c66e253d3a96f6b08a5580387859652aa2 100644
+index b153247b4be38e8ecaf3df64db55df88b7501cfd..337fda9f87ece1fc2264ae6a2af2b7abbb23d788 100644
 --- a/src/main/java/net/minecraft/world/entity/LivingEntity.java
 +++ b/src/main/java/net/minecraft/world/entity/LivingEntity.java
-@@ -3932,6 +3932,19 @@ public abstract class LivingEntity extends Entity implements Attackable {
+@@ -3938,6 +3938,19 @@ public abstract class LivingEntity extends Entity implements Attackable {
      }
  
      // Paper start - Make shield blocking delay configurable