SPIGOT-5930: Add PlayerRespawnEvent#isAnchorSpawn

By: md_5 <git@md-5.net>

paper-server/nms-patches/PlayerList.patch

@@ -475,7 +475,7 @@
 +            }
 +
 +            Player respawnPlayer = cserver.getPlayer(entityplayer1);
-+            PlayerRespawnEvent respawnEvent = new PlayerRespawnEvent(respawnPlayer, location, isBedSpawn);
++            PlayerRespawnEvent respawnEvent = new PlayerRespawnEvent(respawnPlayer, location, isBedSpawn && !flag2, flag2);
 +            cserver.getPluginManager().callEvent(respawnEvent);
 +
 +            location = respawnEvent.getRespawnLocation();