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/0037-Player-affects-spawning-API.patch

@@ -21,7 +21,7 @@ index 3126e8cab3c40e3af47f4c8925e1c6a9523309ba..3207166061bf9c4d7bf3f38e5a9f7aff
      public static Predicate<Entity> withinDistance(double x, double y, double z, double max) {
          double d4 = max * max;
 diff --git a/src/main/java/net/minecraft/world/entity/Mob.java b/src/main/java/net/minecraft/world/entity/Mob.java
-index a61f25425893024571a85cf563ec41cfc7b52325..0e88a2212435ff70b5ee661de3977df2b456b29b 100644
+index c8ff4b01186f924473b9ffde948d7f0573e8d56f..426fa1798087ab1fb4198bd036f498606dce7c3f 100644
 --- a/src/main/java/net/minecraft/world/entity/Mob.java
 +++ b/src/main/java/net/minecraft/world/entity/Mob.java
 @@ -907,7 +907,7 @@ public abstract class Mob extends LivingEntity implements EquipmentUser, Targeti