Add vdc volume getStorageSize

StorageStatsManager.getTotalBytes currently takes the size of /data and
rounds up to known probable sizes to guess the size of internal storage.
This is not always correct.

Instead, find the device /data is on and get the size of that device.
This should give a more accurate answer.

Bug: 295358118
Test: vdc volume getStorageSize returns storage size
Change-Id: I907892041b1ce2cd72092a9877ac34c12bf3f254
diff --git a/VoldNativeService.cpp b/VoldNativeService.cpp
index 601323f..6e795ed 100644
--- a/VoldNativeService.cpp
+++ b/VoldNativeService.cpp
@@ -946,5 +946,10 @@
     return translateBool(destroy_dsu_metadata_key(dsuSlot));
 }
 
+binder::Status VoldNativeService::getStorageSize(int64_t* storageSize) {
+    ENFORCE_SYSTEM_OR_ROOT;
+    return translate(GetStorageSize(storageSize));
+}
+
 }  // namespace vold
 }  // namespace android