Update iterators during aapt2 diff

A recent change broke aapt2 diff. We need to update the iterators when
an package, type, or entry is not missing from either APK.

Bug: 184066458
Test: `aapt2 diff` with framework before and after staging changes
Change-Id: I9138b9bd80aec24488feca6e06be1d7cf5775290
diff --git a/tools/aapt2/Debug.cpp b/tools/aapt2/Debug.cpp
index 351e420..77c0872 100644
--- a/tools/aapt2/Debug.cpp
+++ b/tools/aapt2/Debug.cpp
@@ -300,6 +300,10 @@
             break;
         }
 
+        if (entry->visibility.staged_api) {
+          printer->Print(" STAGED");
+        }
+
         if (entry->overlayable_item) {
           printer->Print(" OVERLAYABLE");
         }