sync: implement directory sync for mod times and metadata

Directory mod times are synced by default if the backend is capable
and directory metadata is synced if the --metadata flag is provided
and the backend is capable.

This updates the bisync golden tests also which were affected by
--dry-run setting of directory modtimes.

Fixes #6685

cmd/move/move.go

@@ -55,6 +55,14 @@ whether rclone lists the destination directory or not.  Supplying this
 option when moving a small number of files into a large destination
 can speed transfers up greatly.
 
+Rclone will sync the modification times of files and directories if
+the backend supports it. If metadata syncing is required then use the
+|--metadata| flag.
+
+Note that the modification time and metadata for the root directory
+will **not** be synced. See https://github.com/rclone/rclone/issues/7652
+for more info.
+
 **Important**: Since this can cause data loss, test first with the
 |--dry-run| or the |--interactive|/|-i| flag.