Compute app data size in case of fragile user data

If an app has fragile user data, compute the total app data size to suggest user if they want to keep the data while uninstalling.

Bug: 182205982
Test: builds successfully
Test: No CTS Tests. Flag to use new app is turned off by default

Change-Id: I592a24ea85ca4769e239610a9b2de150d89a1499