SPIGOT-3496, MC-92282: Set mob type of mob-spawner reverts after single spawn wave.

Fixes CreatureSpawner.setSpawnedType and a vanilla issue related to
setting the mob type of a mob-spawner via spawn_egg.

nms-patches/MobSpawnerAbstract.patch

@@ -1,6 +1,14 @@
 --- a/net/minecraft/server/MobSpawnerAbstract.java
 +++ b/net/minecraft/server/MobSpawnerAbstract.java
-@@ -102,7 +102,7 @@
+@@ -32,6 +32,7 @@
+     public void setMobName(@Nullable MinecraftKey minecraftkey) {
+         if (minecraftkey != null) {
+             this.spawnData.b().setString("id", minecraftkey.toString());
++            this.mobs.clear(); // CraftBukkit - SPIGOT-3496, MC-92282
+         }
+ 
+     }
+@@ -102,7 +103,7 @@
                              ((EntityInsentient) entity).prepare(world.D(new BlockPosition(entity)), (GroupDataEntity) null);
                          }