Add cache mechanism for secondary users in Storage

To prevent from the flicker happening, the size info for secondary users
will be cached.

Bug: 220259287
Test: manual test
1) Create secondary user
2) Finish setup flow
3) Install any types of apps and try to change the storage size
4) Navigate to Settings > Storage
5) Observe the storage size and progress bar, they should have animation
   when storage size info updated.

Change-Id: Iff706b20446603f08334a0b782dd505ca78bdab2