Improve scanner (#1054)

* Handle subdirectories without rx permission correctly
Allow ogg files w/o metadata, having taglib behave more like ffmpeg

* Fix test for walk_dir_tree, fix full reading of files in permission-
constrained directories, allow directories with leading ellipses

* Sorted directory traversal is preferred, and cleanup tests

* Small refactoring to clean-up `loadDir` function and to remove some "warnings" from IntelliJ

Co-authored-by: Deluan <deluan@navidrome.org>

scanner/metadata/taglib.go

@@ -51,7 +51,6 @@ func (e *taglibExtractor) extractMetadata(filePath string) (*taglibMetadata, err
 	md.tags, err = taglib.Read(filePath)
 	if err != nil {
 		log.Warn("Error reading metadata from file. Skipping", "filePath", filePath, err)
-		return nil, errors.New("error reading tags")
 	}
 	md.hasPicture = hasEmbeddedImage(filePath)
 	return md, nil