Re-apply "Refactor walkDirTree to use fs.FS" but remove context cancelation logic.

This reverts commit 6b3b4d83ffcf273b01985709c8bc5df12bbb8286.

scanner/walk_dir_tree.go

@@ -42,12 +42,6 @@ func walkDirTree(ctx context.Context, fsys fs.FS, rootFolder string) (<-chan dir
 }
 
 func walkFolder(ctx context.Context, fsys fs.FS, rootPath string, currentFolder string, results chan<- dirStats) error {
-	select {
-	case <-ctx.Done():
-		return nil
-	default:
-	}
-
 	children, stats, err := loadDir(ctx, fsys, currentFolder)
 	if err != nil {
 		return err