Clear bossbars & entity attributes on server switching (#4278)

* This ensures bossbars are cleared on server switch. Additionally, this clears the EntityCache - which should resolve issues around air supply/hearts persisting visually.

* - Also reset attributes on server switch, aswell as air

core/src/main/java/org/geysermc/geyser/entity/type/player/SessionPlayerEntity.java

@@ -254,4 +254,17 @@ public class SessionPlayerEntity extends PlayerEntity {
     public UUID getTabListUuid() {
         return session.getAuthData().uuid();
     }
+
+    public void resetMetadata() {
+        // Reset all metadata to their default values
+        // This is used when a player respawns
+        this.initializeMetadata();
+
+        // Reset air
+        this.resetAir();
+    }
+
+    public void resetAir() {
+        this.setAirSupply(getMaxAir());
+    }
 }

core/src/main/java/org/geysermc/geyser/session/cache/EntityCache.java

@@ -162,4 +162,9 @@ public class EntityCache {
     public List<Tickable> getTickableEntities() {
         return tickableEntities;
     }
+
+    public void removeAllBossBars() {
+        bossBars.values().forEach(BossBar::removeBossBar);
+        bossBars.clear();
+    }
 }

core/src/main/java/org/geysermc/geyser/translator/protocol/java/JavaLoginTranslator.java

@@ -64,12 +64,17 @@ public class JavaLoginTranslator extends PacketTranslator<ClientboundLoginPacket
             DimensionUtils.switchDimension(session, fakeDim);
 
             session.getWorldCache().removeScoreboard();
+
+            // Remove all bossbars
+            session.getEntityCache().removeAllBossBars();
+            // Remove extra hearts, hunger, etc.
+            entity.getAttributes().clear();
+            entity.resetMetadata();
         }
+
         session.setWorldName(spawnInfo.getWorldName());
         session.setLevels(packet.getWorldNames());
-
         session.setGameMode(spawnInfo.getGameMode());
-
         String newDimension = spawnInfo.getDimension();
 
         boolean needsSpawnPacket = !session.isSentSpawnPacket();
@@ -81,9 +86,7 @@ public class JavaLoginTranslator extends PacketTranslator<ClientboundLoginPacket
 
             // It is now safe to send these packets
             session.getUpstream().sendPostStartGamePackets();
-        }
-
-        if (!needsSpawnPacket) {
+        } else {
             SetPlayerGameTypePacket playerGameTypePacket = new SetPlayerGameTypePacket();
             playerGameTypePacket.setGamemode(EntityUtils.toBedrockGamemode(spawnInfo.getGameMode()).ordinal());
             session.sendUpstreamPacket(playerGameTypePacket);