Update API: initial support

Initial pieces of the Update API callback framework.

- move the status callback params to a new object, UpdateEngineStatus to
allow for the easier addition of new params in the future.
- switch the IUpdateEngineStatusCallback to provide a
ParcelableUpdateEngineStatus instead of a series of individual params
- move the various GetStatus() methods to use the UpdateEngineStatus
object instead of a series of params (which will need future expansion)
- Add current and new product/os versions to both the UpdateEngineStatus
and the ParcelableUpdateEngineStatus.

Bug: 64808702
Test: unit tests, and performing OTAs via a test app calling
  IUpdateEngine::AttemptUpdate() via UpdateManager::performUpdateNow()

Change-Id: I53f66f3511049f0809855814e1e758023cd8cc08
(cherry picked from commit 4f96ebf85022837603f2e10100a044d234b7d86f)
diff --git a/mock_service_observer.h b/mock_service_observer.h
index 032f55a..e434eab 100644
--- a/mock_service_observer.h
+++ b/mock_service_observer.h
@@ -24,12 +24,9 @@
 
 class MockServiceObserver : public ServiceObserverInterface {
  public:
-  MOCK_METHOD5(SendStatusUpdate,
-               void(int64_t last_checked_time,
-                    double progress,
-                    update_engine::UpdateStatus status,
-                    const std::string& new_version,
-                    int64_t new_size));
+  MOCK_METHOD1(
+      SendStatusUpdate,
+      void(const update_engine::UpdateEngineStatus& update_engine_status));
   MOCK_METHOD1(SendPayloadApplicationComplete, void(ErrorCode error_code));
 };