Migrate core code to using symfony/filesystem

webmozart/path-util is retained for plugin compatibility, but is dropped in 5.0

src/world/WorldManager.php

@@ -39,7 +39,7 @@ use pocketmine\world\format\io\WorldProviderManager;
 use pocketmine\world\format\io\WritableWorldProvider;
 use pocketmine\world\generator\GeneratorManager;
 use pocketmine\world\generator\InvalidGeneratorOptionsException;
-use Webmozart\PathUtil\Path;
+use Symfony\Component\Filesystem\Path;
 use function array_keys;
 use function array_shift;
 use function assert;