[PM] Add the flag for providing info of APK-in-APEX

Bug: 306329516
Test: m
Change-Id: I9f8f2fcf3c62ebcb36adb8d75f72a16e8d28515b

core/java/android/content/pm/flags.aconfig

@@ -115,3 +115,11 @@ flag {
     description: "Feature flag to fix duplicated PackageManager flag values"
     bug: "314815969"
 }
+
+flag {
+    name: "provide_info_of_apk_in_apex"
+    namespace: "package_manager_service"
+    description: "Feature flag to provide the information of APK-in-APEX"
+    bug: "306329516"
+    is_fixed_read_only: true
+}