[REFACTOR] Move and refactor tests.

Some tests from boot_control_android_unittest only
test logic of UpdatePartitionMetadata. Move them to
dynamic_partition_control_android_unittest.

After moving the test, boot_control_android_unittest
can depend on the MockDynamicPartitionControl (which
is a mocked DynamicPartitionControlInterface) directly
again. It no longer depends on internal implementation
of DynamicPartitionControlAndroid.

Test: unittest
Fixes: 138333673

Change-Id: Idc5f11be98754b8f6d38fcb8604af497e5d86376
diff --git a/dynamic_partition_control_android.h b/dynamic_partition_control_android.h
index 73d7539..dc152cc 100644
--- a/dynamic_partition_control_android.h
+++ b/dynamic_partition_control_android.h
@@ -79,6 +79,8 @@
                              uint32_t target_slot);
 
  private:
+  friend class DynamicPartitionControlAndroidTest;
+
   std::set<std::string> mapped_devices_;
 
   void CleanupInternal(bool wait);