local: fix exclusion of dangling symlinks with -L/--copy-links

Before this fix, a dangling symlink was erroring the sync. It was
writing an ERROR log and causing rclone to exit with an error. The
List method wasn't returning an error though.

This fix makes sure that we don't log or report a global error on a
file/directory that has been excluded.

This feature was first implemented in:

a61d219bc local: fix -L/--copy-links with filters missing directories

Then fixed in:

8d1fff9a8 local: obey file filters in listing to fix errors on excluded files

This commit also adds test cases for the failure modes of those commits.

See #6376

backend/local/local.go

@@ -524,6 +524,10 @@ func (f *Fs) List(ctx context.Context, dir string) (entries fs.DirEntries, err e
 			if f.opt.FollowSymlinks && (mode&os.ModeSymlink) != 0 {
 				localPath := filepath.Join(fsDirPath, name)
 				fi, err = os.Stat(localPath)
+				// Quietly skip errors on excluded files and directories
+				if err != nil && useFilter && !filter.IncludeRemote(newRemote) {
+					continue
+				}
 				if os.IsNotExist(err) || isCircularSymlinkError(err) {
 					// Skip bad symlinks and circular symlinks
 					err = fserrors.NoRetryError(fmt.Errorf("symlink: %w", err))