system df: fix image-size calculations

Fix two bugs in `system df`:

1.  The total size was calculated incorrectly as it was creating the sum
    of all image sizes but did not consider that a) the same image may
    be listed more than once (i.e., for each repo-tag pair), and that
    b) images share layers.

    The total size is now calculated directly in `libimage` by taking
    multi-layer use into account.

2.  The reclaimable size was calculated incorrectly.  This number
    indicates which data we can actually remove which means the total
    size minus what containers use (i.e., the "unique" size of the image
    in use by containers).

NOTE: The c/storage version is pinned back to the previous commit as it
      is buggy.  c/common already requires the buggy version, so use a
      `replace` to force/pin.

Fixes: #16135
Signed-off-by: Valentin Rothberg <vrothberg@redhat.com>

vendor/github.com/containers/common/pkg/hooks/monitor.go

@@ -15,16 +15,16 @@ import (
 // first is written after the watchers are established and the second
 // when this function exits.  The expected usage is:
 //
-//   ctx, cancel := context.WithCancel(context.Background())
-//   sync := make(chan error, 2)
-//   go m.Monitor(ctx, sync)
-//   err := <-sync // block until writers are established
-//   if err != nil {
-//     return err // failed to establish watchers
-//   }
-//   // do stuff
-//   cancel()
-//   err = <-sync // block until monitor finishes
+//	ctx, cancel := context.WithCancel(context.Background())
+//	sync := make(chan error, 2)
+//	go m.Monitor(ctx, sync)
+//	err := <-sync // block until writers are established
+//	if err != nil {
+//	  return err // failed to establish watchers
+//	}
+//	// do stuff
+//	cancel()
+//	err = <-sync // block until monitor finishes
 func (m *Manager) Monitor(ctx context.Context, sync chan<- error) {
 	watcher, err := fsnotify.NewWatcher()
 	if err != nil {