Implement swimming/gliding including AABB recalculation (#4446)

- The following events have been added:
  - PlayerToggleGlideEvent
  - PlayerToggleSwimEvent
- The following API methods have been added:
  - Entity->getSize()
  - Living->isSwimming()
  - Living->setSwimming()
  - Living->isGliding()
  - Living->setSwimming()
  - Player->toggleSwim()
  - Player->toggleGlide()

src/event/player/PlayerToggleGlideEvent.php

@@ -0,0 +1,40 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+*/
+
+declare(strict_types=1);
+
+namespace pocketmine\event\player;
+
+use pocketmine\event\Cancellable;
+use pocketmine\event\CancellableTrait;
+use pocketmine\player\Player;
+
+class PlayerToggleGlideEvent extends PlayerEvent implements Cancellable{
+	use CancellableTrait;
+
+	public function __construct(Player $player, protected bool $isGliding){
+		$this->player = $player;
+	}
+
+	public function isGliding() : bool{
+		return $this->isGliding;
+	}
+}

src/event/player/PlayerToggleSwimEvent.php

@@ -0,0 +1,40 @@
+<?php
+
+/*
+ *
+ *  ____            _        _   __  __ _                  __  __ ____
+ * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
+ * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
+ * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
+ * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * @author PocketMine Team
+ * @link http://www.pocketmine.net/
+ *
+ *
+*/
+
+declare(strict_types=1);
+
+namespace pocketmine\event\player;
+
+use pocketmine\event\Cancellable;
+use pocketmine\event\CancellableTrait;
+use pocketmine\player\Player;
+
+class PlayerToggleSwimEvent extends PlayerEvent implements Cancellable{
+	use CancellableTrait;
+
+	public function __construct(Player $player, protected bool $isSwimming){
+		$this->player = $player;
+	}
+
+	public function isSwimming() : bool{
+		return $this->isSwimming;
+	}
+}