updater_sample: Add streaming to PayloadSpec

PayloadSpec
- add streaming generator and tests
- fix sample.json
- fix tests
- rename PackagePropertyFiles to PackageFiles, it has info
  not only about property files, and new name is shorter

Bug: 77148467
Test: `mmma -j bootable/recovery/updater_sample`
Change-Id: I9c1206c07c37183f13d3c25940f12981ca85b1b4
Signed-off-by: Zhomart Mukhamejanov <zhomart@google.com>
diff --git a/updater_sample/src/com/example/android/systemupdatersample/ui/MainActivity.java b/updater_sample/src/com/example/android/systemupdatersample/ui/MainActivity.java
index 8507a9e..9f1e5d1 100644
--- a/updater_sample/src/com/example/android/systemupdatersample/ui/MainActivity.java
+++ b/updater_sample/src/com/example/android/systemupdatersample/ui/MainActivity.java
@@ -297,7 +297,7 @@
     }
 
     /**
-     * Helper class to delegate UpdateEngine callbacks to MainActivity
+     * Helper class to delegate {@code update_engine} callbacks to MainActivity
      */
     class UpdateEngineCallbackImpl extends UpdateEngineCallback {
         @Override